HP P6000 Continuous Access Implementation Guideh20628. · HPP6000ContinuousAccess...

HP P6000 Continuous AccessImplementation Guide

AbstractThis guide explains the major factors in designing a successful disaster recovery solution using HP P6000 Continuous Access.In addition to explaining how distance and bandwidth affect performance and cost, this guide describes optional configurationsand key planning for your operating systems, applications, and arrays.

This guide is intended for IT managers, business managers, and storage area network (SAN) architects working in environmentsthat include any EVA model (EVA3000/5000, EVA4x00/6x00/8x00, EVA4400, EVA6400/8400, P6300/P6500).

IMPORTANT: General references to HP P6000 Continuous Access may also refer to earlier versions of HP Continuous AccessEVA. P6000 is the new branding for the Enterprise Virtual Array product family.

HP Part Number: T3680-96431Published: July 2012Edition: 10

© Copyright 2008, 2012 Hewlett–Packard Development Company, L.P.

Confidential computer software. Valid license from HP required for possession, use or copying. Consistent with FAR 12.211 and 12.212, CommercialComputer Software, Computer Software Documentation, and Technical Data for Commercial Items are licensed to the U.S. Government undervendor's standard commercial license.

Warranty

The information contained herein is subject to change without notice. The only warranties for HP products and services are set forth in the expresswarranty statements accompanying such products and services. Nothing herein should be construed as constituting an additional warranty. HP shallnot be liable for technical or editorial errors or omissions contained herein.

Acknowledgements

Microsoft® and Windows® are U.S. registered trademarks of Microsoft Corporation.

UNIX® is a registered trademark of The Open Group.

Linux® is a registered trademark of Linus Torvalds in the U.S. and other countries.

Contents1 HP P6000 Continuous Access .....................................................................7

Features..................................................................................................................................7Remote replication concepts.......................................................................................................8

Write modes ......................................................................................................................8DR groups ..........................................................................................................................8DR group write history log.....................................................................................................9Managed sets.....................................................................................................................9Failover............................................................................................................................10Failsafe mode....................................................................................................................10Failsafe on Link-down/Power-up...........................................................................................11

Implementation checklist..........................................................................................................112 Designing a remote application solution......................................................14

Tools for gathering SAN data...................................................................................................14Choosing the remote site.........................................................................................................14

High availability................................................................................................................15Recovery time objective..................................................................................................15

Disaster tolerance..............................................................................................................15Disaster tolerance and distance.......................................................................................15Determining the minimum separation distance...................................................................15

Distance and performance..................................................................................................16Latency factor...............................................................................................................16Determining intersite latency...........................................................................................17Evaluating intersite latency.............................................................................................17

Cost.................................................................................................................................17Choosing the intersite link........................................................................................................17

Distance...........................................................................................................................17Recovery point objective.....................................................................................................18Bandwidth .......................................................................................................................18Bandwidth capacity and peak loads....................................................................................18

Determining the critical sample period.............................................................................19Sizing bandwidth for synchronous replication....................................................................19Sizing bandwidth for asynchronous replication..................................................................20

Evaluating bandwidth capacity............................................................................................20Choosing a write mode...........................................................................................................20

Asynchronous write mode...................................................................................................21Basic asynchronous mode..............................................................................................21Enhanced asynchronous mode........................................................................................21

Synchronous mode.............................................................................................................22Maintaining DR group I/O consistency.................................................................................22

3 Planning the remote replication fabric.........................................................23Basic dual-fabric configuration.................................................................................................23

Basic configuration limits....................................................................................................23Basic configuration rules.....................................................................................................24Extended fabric using long-distance GBICs and SFPs..............................................................24Extended fabric using WDM...............................................................................................24

Fabric to IP............................................................................................................................25Fibre Channel-to-IP.............................................................................................................25

FC-to-IP configuration limits.............................................................................................25FC-to-IP configuration rules.............................................................................................25

Configurations with application failover.....................................................................................26

Contents 3

HP Cluster Extension ..........................................................................................................26HP Metrocluster Continuous Access......................................................................................27HP Continentalcluster..........................................................................................................27

Reduced-availability configurations...........................................................................................27Single-fabric configuration..................................................................................................27Single-switch configuration..................................................................................................28Single-HBA configuration....................................................................................................29

Advanced configurations.........................................................................................................29Five-fabric configuration......................................................................................................29Six-fabric configuration.......................................................................................................32

4 Planning the array configuration.................................................................35Planning disk groups...............................................................................................................35

Determining the number of disk groups.................................................................................35Specifying disk group properties..........................................................................................35

Planning DR groups................................................................................................................36DR group guidelines ..........................................................................................................36

Implicit LUN transition and HP P6000 Continuous Access...................................................37DR group name guideline..............................................................................................37Increasing the size of the write history log file in enhanced or basic asynchronous mode........38

DR groups with FATA or SAS Midline drives...........................................................................38Planning the data replication protocol.......................................................................................38

Selecting the data replication protocol..................................................................................39Data replication protocol performance considerations.............................................................40Tunnel thrash.....................................................................................................................41

Planning for DR group write history logs....................................................................................42Logging in synchronous or basic asynchronous mode..............................................................42Logging in enhanced asynchronous mode.............................................................................42Normalization...................................................................................................................43DR group write history log size............................................................................................43

Write history log size in synchronous or basic asynchronous mode.......................................44Write history log file size in enhanced asynchronous mode.................................................44Incorrect error message for minimum asynchronous replication log size................................44Log size displayed incorrectly when creating DR groups in a mixed controller softwareenvironment .................................................................................................................44

DR group write history log location......................................................................................44Planning replication relationships..............................................................................................46

Bidirectional replication......................................................................................................46System fan-out replication....................................................................................................47Fan-in replication...............................................................................................................48Cascaded replication.........................................................................................................49

5 Planning the solution.................................................................................50Operating system considerations..............................................................................................50

Supported operating systems...............................................................................................50Operating system capabilities..............................................................................................50

Boot from SAN.............................................................................................................50Bootless failover............................................................................................................50

6 Implementing remote replication.................................................................51Remote replication configurations..............................................................................................51Verifying array setup...............................................................................................................51

Installation checklist............................................................................................................51Verifying Fibre Channel switch configuration..........................................................................51

B-series switch configuration............................................................................................52C-series switch configuration...........................................................................................52

4 Contents

H-series switch configuration...........................................................................................54M-series switch configuration..........................................................................................54

Verifying cabling...............................................................................................................54Changing host port data replication settings..........................................................................56

Verifying path status......................................................................................................57Installing replication licenses....................................................................................................58Installing HP P6000 Replication Solutions Manager (optional)......................................................58

DC-Management and HP P6000 Continuous Access..............................................................58Creating fabrics and zones......................................................................................................58

Fabric configuration drawings..............................................................................................58Two-fabric configuration.................................................................................................59HP P6000 Command View management connections in five-fabric and six-fabricconfigurations...............................................................................................................61A single physical fabric..................................................................................................66Dual physical fabric with six zones..................................................................................67

Best practices for using zones with HP P6000 Continuous Access.............................................69Zoning management servers...........................................................................................70

Zoning best practices for traffic and fault isolation..................................................................70Recommended single-fabric zoning configurations..................................................................71Recommended dual-fabric zoning configurations....................................................................80FCIP gateway zoning configurations.....................................................................................95

Configuring hosts....................................................................................................................96Configuring disk groups for remote replication............................................................................96Creating and presenting source virtual disks...............................................................................96

Selecting a preferred controller ...........................................................................................97Using the failover/failback setting........................................................................................97Using the failover only setting..............................................................................................98Presenting virtual disks........................................................................................................98

Adding hosts .........................................................................................................................98Creating DR groups................................................................................................................98

Specifying virtual disks.......................................................................................................98Adding members to a DR group..........................................................................................99Selecting replication mode..................................................................................................99Specifying DR group write history log location and size .........................................................99

Presenting destination virtual disks..........................................................................................100Backing up the configuration..................................................................................................100Setting up remote and standby management servers.................................................................100Testing failover.....................................................................................................................100

7 Failover and recovery.............................................................................101Failover example..................................................................................................................101Planning for a disaster...........................................................................................................103Failover and recovery procedures...........................................................................................103

Performing failover and recovery........................................................................................104Choosing a failover procedure..........................................................................................104Planned failover...............................................................................................................105

Planned Failover Procedure..........................................................................................107Unplanned failover..........................................................................................................108Recover from failsafe-locked after destination loss.................................................................108Failback to the original source following a planned or unplanned failover...............................110Return operations to new hardware....................................................................................110Recovering from a disk group hardware failure....................................................................113

Failed disk group hardware indicators...........................................................................113Disk group hardware failure on the source array ............................................................114Disk group hardware failure on the destination array.......................................................115

Contents 5

Protecting data from a site failure............................................................................................1168 Operating system procedures...................................................................118

Resuming host I/O after failover.............................................................................................118HP OpenVMS.................................................................................................................118HP Tru64 UNIX................................................................................................................118HP-UX.............................................................................................................................118IBM AIX..........................................................................................................................119Linux..............................................................................................................................119Novell NetWare..............................................................................................................120Sun Solaris.....................................................................................................................120VMware.........................................................................................................................121Windows........................................................................................................................121

Red Hat and SUSE Linux LifeKeeper clusters..............................................................................122Bootless failover using LVM with Linux .....................................................................................122

Source host procedure......................................................................................................122Destination host procedure................................................................................................123

9 Managing remote replication...................................................................124Using remote replication in a mixed array environment..............................................................124Managing merges and normalization......................................................................................124

Throttling a merge I/O after logging..................................................................................124Maintaining I/O performance while merging......................................................................124Preparing for a normalization............................................................................................124

Optimizing performance.......................................................................................................125Load balancing...............................................................................................................125

Backing up replication configuration.......................................................................................126Using HP P6000 Replication Solutions Manager for backups.................................................126Using HP Storage System Scripting Utility to capture your configuration...................................126Keeping a written record of your configuration.....................................................................126

Upgrading controller software................................................................................................12710 Support and other resources...................................................................128

Contacting HP......................................................................................................................128HP technical support........................................................................................................128Subscription service..........................................................................................................128Documentation feedback..................................................................................................128Product feedback.............................................................................................................128

Related information...............................................................................................................128Documentation................................................................................................................128HP websites....................................................................................................................129

Typographical conventions ....................................................................................................129Glossary..................................................................................................131Index.......................................................................................................136

6 Contents

1 HP P6000 Continuous AccessHP P6000 Continuous Access is the remote replication component of HP controller software. Whenthis component is licensed and configured, the controller copies data online, in real time, to aremote array over a SAN. Properly configured, HP P6000 Continuous Access provides adisaster-tolerant storage solution that ensures data integrity and, optionally, data currency RPO ifan array or site fails.Figure 1 (page 7) shows a typical remote replication setup with arrays on local and remote sitesconnected by two linked fabrics. Two ISLs connect the local and remote fabrics.

NOTE: In SAN design terminology, an ISL is also referred to as an interswitch link.

Figure 1 Basic HP P6000 Continuous Access configuration

6. Local/remote fabric—blue1. Local site

7. ISL—blue2. Remote site

8. Local/remote fabric—gold3. LAN connection

9. ISL—gold4. Management server

10. Arrays5. Hosts

FeaturesHP P6000 Continuous Access features include:

• Continuous replication of local virtual disks on remote virtual disks

• Synchronous, basic asynchronous, and enhanced asynchronous replication modes

• Automated failover when used with other cluster software

• Failsafe data protection

• Ability to suspend and resume replication

• Bidirectional replication

• Graphical and command line user interfaces (GUI and CLUI) to simplify replication management

• Automatic suspension of replication if the link between arrays is down.

Features 7

• Support for array-to-array fan-in and fan-out

• HP SCSI FC Compliant Data Replication Protocol (HP SCSI-FCP), a full SCSI protocolimplementation that takes advantage of the exchange-based routing available in fabric switches.For more information, see “Planning the data replication protocol” (page 38).

See the HP P6000 Enterprise Virtual Array Compatibility Reference for more information on remotereplication support by controller software version. See “Documentation” (page 128) for the link tothis document.

NOTE: HP P6000 Continuous Access interacts with HP P6000 Command View or HP P6000Replication Solutions Manager to manage remote replication. To perform replication tasks, HPP6000 Command View and HP P6000 Replication Solutions Manager must be installed on amanagement server. If you are using the array-based management version of HP P6000 CommandView, you cannot perform remote replication tasks.

Remote replication conceptsRemote replication is the continuous copying of data from selected virtual disks on a source (local)array to related virtual disks on a destination (remote) array. Applications continue to run whiledata is replicated in the background. Remote replication requires a fabric connection between thesource and destination arrays and a software connection (DR group) between source virtual disksand destination virtual disks.

Write modesThe remote replication write modes are as follows:

• Asynchronous—The array acknowledges I/O completion before data is replicated on thedestination array. Asynchronous write mode can be basic or enhanced, depending on thesoftware version of the controller.

• Synchronous—The array acknowledges I/O completion after the data is cached on both thelocal and destination arrays.

For more information on write modes, see “Choosing a write mode” (page 20).

DR groupsA DR group is a logical group of virtual disks in a remote replication relationship between twoarrays. Hosts write data to the virtual disks in the source array, and the array copies the data tothe virtual disks in the destination array. I/O ordering is maintained across the virtual disks in aDR group, ensuring I/O consistency on the destination array in the event of a failure of the sourcearray. The virtual disks in a DR group fail over together, share a write history log (DR group log),and preserve write order within the group.Figure 2 (page 9) illustrates the replication of one DR group between a source array and adestination array. For more information, see “Planning DR groups” (page 36).

8 HP P6000 Continuous Access

Figure 2 DR group replication

6. Destination array1. Host server

7. Source virtual disk2. Fibre Channel switch

8. Destination virtual disk3. Host I/O

9. DR group4. Replication writes

5. Source array

DR group write history logThe DR group write history log is a virtual disk that stores a DR group's host write data. The log iscreated when you create the DR group. Once the log is created, it cannot be moved. For moreinformation, see “Planning for DR group write history logs” (page 42).

Managed setsManaged sets are a feature of HP P6000 Replication Solutions Manager. A managed set is anamed collection of resources banded together for convenient management. A managed set cancontain DR groups, enabled hosts, host volumes, storage systems, or virtual disks.Performing an action on a managed set performs the action on all members of the set. For example,the managed set Sales_Disks might include two virtual disks, West_Sales and East_Sales. If youperform the New Snapshot action on the managed set Sales_Disks, the interface creates a newsnapshot of West_Sales and a new snapshot of East_Sales.

Remote replication concepts 9

NOTE: Managed sets are simply a feature that enables you to manage multiple resources easily.They do not contribute to the data consistency of a DR group. Write order consistency is maintainedat the DR group level.

In managed sets:

• All resources, or members, in a single managed set must be of the same type (for example,all virtual disks).

• You can add a specific resource to more than one managed set.

• You can add resources on more than one array to a managed set.

• You should create separate managed sets for DR groups so that if a failover occurs, you canperform the actions that correspond to the changed source/destination role of the managedset members.

FailoverIn HP P6000 Continuous Access replication, failover reverses replication direction for a DR group.The destination array assumes the role of the source, and the source array assumes the role of thedestination. For example, if a DR group on array A is replicating to array B, a failover would causedata for the DR group to be replicated from array B to array A.You can failover a single DR group or you can failover multiple DR groups with a single commandusing a managed set. When you specify a failover action for a specific managed set, the failoveroccurs for all DR groups contained in the specified managed set. Without managed sets, you mustfail over each DR group individually. For more information on failover settings, see “Creating andpresenting source virtual disks” (page 96).

NOTE: Failover can take other forms:• Controller failover—The process that occurs when one controller in a pair assumes the workload

of a failed or redirected controller in the same array.• Fabric or path failover—I/O operations transfer from one fabric or path to another.This guide describes the failover of DR groups and managed sets. It does not address controllerfailover within a cabinet, or path, or fabric failover, because redundancy is assumed.

Failsafe modeFailsafe mode is only available when a DR group is being replicated in synchronous mode andspecifies how host I/O is handled if data cannot be replicated between the source and destinationarray. The failsafe mode can be on of the following:

• Failsafe enabled—All host I/O to the DR group is stopped if data cannot be replicated betweenthe source array and destination array. This ensures that both arrays will always contain thesame data (RPO of zero). A failsafe-enabled DR group can be in one of two states:

◦ Locked (failsafe-locked)—Host I/O and remote replication have stopped because datacannot be replicated between the source and destination array.

◦ Unlocked (failsafe-unlocked)—Host I/O and remote replication have resumed oncereplication between the arrays is re-established.

• Failsafe disabled—If replication of data between the source and destination array is interrupted,the host continues writes to the source array, but all remote replication to the destination arraystops and I/Os are put into the DR group write history log until remote replication isre-established.


NOTE: Failsafe mode is available only in synchronous write mode. Host I/O can be recoveredby changing affected DR groups from failsafe-enabled mode to failsafe-disabled mode. This actionwill begin logging of all incoming writes to the source member of the Data Replication group.

Failsafe on Link-down/Power-upFailsafe on Link-down/Power-up is a setting that specifies whether or not virtual disks in a DR groupare automatically presented to hosts after a power-up (reboot) of the source array when the linksto the destination array are down and the DR group is not suspended. This prevents a situationwhere the virtual disks in a DR group are presented to servers on the destination array followinga failover and then the virtual disks on the source array are also presented when it reboots.Values for Failsafe on Link-down/Power-up are as follows:

• Enabled—Virtual disks in a source DR group are not automatically presented to hosts. This isthe default value assigned to a DR group when it is created. This behavior is called presentationblocking and provides data protection under several circumstances. Host presentation remainsblocked until the destination array becomes available (and can communicate with the sourcearray) or until the DR group is suspended.

• Disabled—Virtual disks in a source DR group are automatically presented to hosts after acontroller reboot.

This feature can be disabled only after the DR group is created. See the HP P6000 EnterpriseVirtual Array Compatibility Reference to determine if your controller software supports disablingthis feature.

Implementation checklistTable 1 (page 11) provides an overview and checklist of the primary tasks involved in planningand implementing an HP P6000 Continuous Access environment. Table 1 (page 11) also providesa link from each task to more detail elsewhere in this guide. Use the checklist to record your progressas you perform each task. For links to the documentation identified, see “Documentation” (page 128).

IMPORTANT: Table 1 (page 11) is provided as an aid for implementing HP P6000 ContinuousAccess. It should be used in conjunction with the remaining content of this guide. If you are installingyour first HP P6000 Continuous Access environment, before starting the installation read throughthis entire guide to ensure that you implement HP P6000 Continuous Access successfully.

Table 1 HP P6000 Continuous Access implementation checklist

Planning tasks (Perform before implementing HP P6000 Continuous Access)

“Designing a remote application solution” (page 14)Things you will need:Appropriate tool for gathering SAN latency data. See “Tools for gathering SAN data” (page 14).__ Evaluate all factors impacting selection of a remote site.__ Define the RTO.__ Consider the impact of intersite latency on all applications.

“Bandwidth capacity and peak loads” (page 18)Things you will need:Appropriate tool for gathering I/O data. See “Tools for gathering SAN data” (page 14).__ Monitor and record sustained I/O load.__ Monitor and record burst I/O load.

“Choosing the intersite link” (page 17)Things you will need:

Implementation checklist 11

Table 1 HP P6000 Continuous Access implementation checklist (continued)

Appropriate tool for gathering bandwidth data. See “Tools for gathering SAN data” (page 14).__ Evaluate all factors impacting selection of the ISL.__ Define the RPO.__ Select a write mode that supports the RPO.__ Verify that the ISL meets bandwidth and Quality of Service (QoS) requirements for HP P6000 Continuous Access.

“Planning the remote replication fabric” (page 23)Things you will need:

• HP SAN Design Reference Guide

• Appropriate switch best practices guide

__ Select the desired fabric configuration.__ Ensure all SAN switches are compatible.__ Observe any switch-specific requirements for HP P6000 Continuous Access.

“Planning the array configuration” (page 35)Things you will need:

• HP Enterprise Virtual Array Configuration Best Practices White Paper


• HP P6000 Enterprise Virtual Array Compatibility Reference

__ Ensure that the array configuration meets best practices guidelines.__ Ensure that the array has adequate capacity for DR group write history logs.__ Ensure that only supported arrays are used in each HP P6000 Continuous Access relationship.

Implementation tasks

“Implementing remote replication” (page 51)__ Verify array setup.__ Ensure all cabling requirements are met when connecting each array to the fabric.__ Install replication licenses and replication management software.

“Verifying Fibre Channel switch configuration” (page 51)__ Check current switch configuration settings.__ Change settings as required. See switch documentation for procedures.

“Creating fabrics and zones” (page 58)Things you will need:


__ Review fabric and zoning requirements for HP P6000 Continuous Access.__ Create the desired fabrics and zones.

“Configuring disk groups for remote replication” (page 96)__ Determine the number of disk groups required to support application data being replicated.__ Create and present the virtual disks.

“Creating DR groups” (page 98)__ Create the necessary DR groups, ensuring that all DR group guidelines are met.__ Select the desired replication mode.__ Select the DR group write history log location and size.__ Present the destination virtual disks.

“Failover and recovery” (page 101)__ Create a disaster plan.


Table 1 HP P6000 Continuous Access implementation checklist (continued)

__ Select a failover and recovery procedure.__ Observe all operating system-specific failover and recovery procedures.__ Test failover and recovery.

Implementation checklist 13

2 Designing a remote application solutionThis chapter describes important factors involved in designing a successful remote replicationsolution using HP P6000 Continuous Access:

• “Choosing the remote site” (page 14)

• “Choosing the intersite link” (page 17)

• “Choosing a write mode” (page 20)

Tools for gathering SAN dataA critical task in designing your HP P6000 Continuous Access implementation is gathering andanalyzing the characteristics of your current SAN operating environment. This includes parameterssuch as I/O patterns, bandwidth, and latency. This data enables you to design a replicationconfiguration that matches your SAN environment.

NOTE: Before implementing an HP P6000 Continuous Access replication solution, contact yourauthorized HP account representative for assistance. They can provide you with access to the toolsmentioned in this section.

The following tools are available to assist you in gathering SAN data:

• HP Essentials Data Replication Designer—A GUI-based automated tool for gathering SANdata. The Data Replication Designer gathers the SAN data and copies it to the ReplicationWorkload Profiler (RWP), an interactive spreadsheet used by HP to evaluate how well HPP6000 Continuous Access will work within your current SAN environment. Complete instructionsfor using the designer are included in the HP Essentials Data Replication Designer 1.0 UserGuide.

NOTE: For more information on support for Data Replication Designer, go to the HP SPOCKwebsite: http://www.hp.com/storage/spock.

• Replication Workload Profiler—An interactive spreadsheet that calculates replicationrequirements based on current SAN data. On Windows, the Data Replication Designerautomatically populates the RWP with SAN data. On other operating systems, it is necessaryto populate the RWP manually with the SAN data. The RWP and other spreadsheets used forgathering SAN data are available from your authorized HP account representative.

• HP Command View EVAPerf—Gathers performance data on the array. Complete instructionsfor using HP Command View EVAPerf are included in the HP P6000 Command View UserGuide. For more information, see “Documentation” (page 128).

Choosing the remote siteThe location of the remote site can be the most important and the most complex decision inimplementing a remote replication solution. It requires an analysis of competing objectives:

• “High availability” (page 15)—The business need for continuous access to data withoutdowntime

• “Disaster tolerance” (page 15)—The business need for data to survive a site disaster

• “Distance and performance” (page 16)—The effect of distance on replication throughput anddata currency

• “Cost” (page 17)—The cost of data transmission lines between sitesThis section examines these objectives in detail.

14 Designing a remote application solution

http://www.hp.com/storage/spock

High availabilityHigh availability reduces the risk of downtime through redundant systems, software, and IT processeswith no SPOF. HP P6000 Continuous Access contributes to high availability by providing redundantdata. Products such as HP Metrocluster and HP Cluster Extensions provide highly availableapplications. For more information about these and other high-availability products, see the HPwebsite:http://docs.hp.com/en/ha.htmlIf your business needs high availability, but does not require disaster tolerance, local and remotesites can be in the same room, building, or city. Distance and its effect on cost and performanceare not important issues.

Recovery time objectiveThe RTO is a measure of high availability—it is the length of time the business can afford to spendreturning an application to operation. It includes the time required to detect the failure, to fail overthe storage, and to restart the application on a new server. RTO is usually measured in minutes orhours, and, occasionally, in days.A shorter RTO increases the need for products that automatically fail over applications and data.HP Metrocluster and HP Continentalcluster work with HP P6000 Command View to provideapplication and data failover in ServiceGuard HP-UX environments. HP Cluster Extension providessimilar functionality for Microsoft Windows clusters and ServiceGuard on Linux environments. Formore information on remote replication configurations with cluster software, see “Configurationswith application failover” (page 26).

Disaster toleranceIf your business requires disaster tolerance, the location of the remote site is critical. Distance andits relationship to cost and performance are major concerns.

Disaster tolerance and distanceDisaster tolerance uses redundant components to enable the continued operation of criticalapplications during a site disaster. When two sites are separated by a distance greater than thepotential size and scope of a disaster, each site is protected from a disaster on or near the othersite. HP P6000 Continuous Access enables applications to build two copies of application dataat sites that are far enough apart to provide disaster tolerance.

Determining the minimum separation distanceIn disaster-tolerant solutions, the size of the threat to each site determines the required distancebetween local and remote sites. The threat radius is the distance from the center of a threat to theoutside perimeter of that threat. Figure 3 (page 16) shows sample threat radii for common threatclassifications. The required distance between the two sites is the sum of the maximum threat radiusfor each site when subjected to a common threat.

Choosing the remote site 15

http://docs.hp.com/en/ha.html

Figure 3 Threat categories based on radius

1. Regional threat (radius between 10 and 100 kilometers, affecting up to 314,000 square kilometers)

2. Metropolitan threat (radius between 1 and 10 kilometers, affecting up to 314 square kilometers)

3. Local threat (radius less than 1 kilometer, affecting 3 square kilometers)

When determining the threat radius, identify the threats to both sites and the specific threat range.Sample threats include tornados, fires, flood, power loss, chemical incidents, earthquakes,hurricanes, and typhoons. Consider the shape, center, and direction of each threat. For example,if severe storms tend to travel in a specific direction, you can place the second site perpendicularto the expected route of travel from the first site. If multiple threats range in size and severity,develop your solution for the largest threat.

Distance and performanceHP P6000 Continuous Access can move data at extreme distances. However, the speed of lightin fiber optic cables (1 millisecond per 100 kilometers, round trip) causes inherent delays, calledlatency. At extreme distances, latency is the limiting factor in replication performance, regardlessof bandwidth. Latency becomes an even larger factor when switched IP networks are used toreplicate data.

IMPORTANT: Intersite latency may impact your applications. You must ensure that all applicationscan accommodate the intersite latency interval. This is important when using synchronous writemode because every write I/O will incur the intersite latency.

Latency factorThe greater the distance, the greater the impact intersite latency has on replication performance.For example, a 1-block write that completes in 0.25 milliseconds without replication takes 0.35milliseconds to complete with synchronous replication and zero distance between copies. Add100 kilometers of cable and the replication of that block takes 1.35 milliseconds. The additionalmillisecond is the time it takes for the data to travel 100 kilometers to the destination array andfor the acknowledgement to travel 100 kilometers back to the source array. Add another 100kilometers of cable, and the same write requires 2.35 milliseconds.

NOTE: When replicating synchronously, the total write I/O service time latency is the sum of thewrite I/O service time on the local array, plus the round-trip network latency, plus the write I/Oservice time on the destination array. On slow links, queuing effects (I/Os waiting in the queuefor transfer over the network) can introduce additional latency, extending the total write I/O servicetime far beyond that imposed by the other factors mentioned.


Table 2 (page 17) lists the intersite one-way latency inherent to other distances.

Table 2 Sample one-way latencies

Point-to-point cable distance in km (miles)One-way latency (ms)

200 (125)1

600 (375)3

1,800 (1,125)9

3,600 (2,250)18

7,200 (4,500)36

12,000 (7,500)60

20,000 (12,500) current maximum limit100

Determining intersite latencyTo determine intersite latency on an existing network, use network utilities such as the pingcommand. Obtain a 24-hour average. See the HP SAN Design Reference Guide for moreinformation about network utilities.

Evaluating intersite latencyThe Data Replication Designer can be used to gather intersite latency data. The designer is supportedon Windows only. See “Tools for gathering SAN data” (page 14) for more information on theData Replication Designer and other tools available for evaluating intersite latency.

CostThe cost associated with transmission lines increases with distance and bandwidth requirements.The cost may prohibit the selection of a favorite site. If the required bandwidth proves too costly,consider moving the remote site closer to the local site or replicating only the most critical data,such as transaction or retransmission logs.

Choosing the intersite linkThe location of the remote site determines the intersite link technologies that meet your distanceand performance requirements. Including distance, the following factors affect bandwidth:• “Distance” (page 17)—The transmission distance supported by specific link technologies

• “Recovery point objective” (page 18)—The acceptable difference between local and remotecopies of data

• “Bandwidth capacity and peak loads” (page 18)—The effect of application peak loads onbandwidth

DistanceHP P6000 Continuous Access supports direct Fibre Channel (FC) and extended Fibre Channel-to-IP(FC-to-IP) links ranging in bandwidth from 2.048 Mb/s to more than 4 Gb/s. The supportedtransmission distance varies with the technology.• Basic fiber supports a maximum of 500 meters at 1 Gb/s; shorter lengths are supported at

higher bandwidths. The distance varies with the speed of the link. For more information, seethe HP SAN Design Reference Guide.

• Fiber with long-distance and very-long-distance GBICs can support up to 200 times the basicfiber distance.

Choosing the intersite link 17

• Fiber with WDM supports up to 500 kilometers.

• FC-to-IP gateways support the longest distances.For detailed descriptions of supported link technologies, see “Planning the remote replicationfabric” (page 23).

NOTE: Regardless of the transmission technology, HP P6000 Continuous Access does not takeinto account the type of media used for the intersite network connection. Acceptable media isdetermined by the quality of the link as described in Part IV, “SAN extension and bridging” of theHP SAN Design Reference Guide.

Recovery point objectiveThe RPO is the amount of data loss that the business can tolerate as a result of a disaster or otherunplanned event requiring failover. RPO is measured in time, and ranges from no time (zero) tohours, or in some instances even days. An RPO of zero means no completed transaction can belost and requires synchronous replication. Note that synchronous replication mode may requiremore bandwidth than asynchronous. For descriptions of synchronous and asynchronous writemodes, see “Choosing a write mode” (page 20).

BandwidthWhen you cannot adjust the distance between sites, you may be able to improve performance byincreasing bandwidth.Consider a low-bandwidth link and a high-bandwidth link that are moving writes containing identicalamounts of data from site A to site B. See Figure 4 (page 18). The writes move through low- andhigh-bandwidth links at the same speed, so the leading edges of both writes arrive simultaneouslyat site B. The upper link in Figure 4 (page 18) is one-third the bandwidth of the lower link, so thebits are three times longer. Because the bits are longer in the low-bandwidth link, the data takesmore time to unload than the data in the high-bandwidth link. The same advantage applies toloading data into a high-bandwidth link compared to a low-bandwidth link.

Figure 4 Bandwidth and I/O rate

1. Site A

2. T3 link (44.5 Mb/s)

3. OC3 link (155 Mb/s)

4. Site B

Bandwidth capacity and peak loadsWith synchronous replication, the intersite link must accommodate the peak write rate of yourapplications. With asynchronous replication, the intersite link must support the peak average write


rate based on the RPO (or over the RPO interval). Insufficient replication bandwidth impacts userresponse time, RPO, or both.

Determining the critical sample periodWorking with large measurement samples can be tedious and problematic. A two-stage approachto data collection generally helps to reduce the effort. In the first stage, the historical write byterate trends are analyzed to determine peak periods that can occur during monthly or yearly businesscycles and daily usage cycles. Once a peak period is identified, a more granular measurement(the second stage in the analysis) can be made to collect detailed one second measurements ofthe I/O write profile. A 1- to 8-hour interval is ideal because the measurements can be easilyimported into a Microsoft Excel worksheet and charted for reduction and analysis.If you have a good understanding of your organization's business cycles, the critical sample periodcan be selected with very little additional data collection or reduction. If the write profile is unknown,then the critical sample period can generally be identified from daily incremental backup volumesor transaction rates from application logs. Setting up a long term collection for trending is generallyimpractical as this could delay the sizing process by several weeks or more.It is imperative that measurement data for all volumes sharing the intersite replication bandwidthis collected over a common time frame so that the aggregate peak can be determined. This isespecially important when selecting the critical sample period.Table 3 (page 19) shows recommended sample rate intervals for various RPOs. Remember thatthe shorter the sample rate interval, the closer the solution will be to meeting your desired RPO.

Table 3 RPO sample rate intervals

Sample rate intervalDesired RPO

1 second0–60 minutes

30 seconds1–2 hours

1 minute2–3 hours

2 minutes3–4 hours

Up to 5 minutes> 4 hours

Sizing bandwidth for synchronous replicationApplication data that is replicated synchronously is highly dependent on link latency because writerequests must be received at the recovery site before the application receives a completion. Writeresponse time in a replicated environment is greatly affected by propagation delays and queuingeffects. Latencies due to propagation delays can generally be measured and are typically fixedfor a given configuration. Latencies due to queuing effects at the link are more difficult to estimate.Propagation delays due to distance can be estimated at 1 millisecond per 100 kilometers to accountfor the round-trip exchange through dark fiber. Most applications easily accommodate an additional1-millisecond of latency when DR sites are separated by a distance of 100 kilometers, a typicalmetro-replication distance. At 500 to 1,000 kilometers, the 5- to 10-millisecond propagation latencyaccounts for 25% to 50% of the 20-millisecond average latency budgeted to applications such asemail. This puts a practical cap for synchronous replication at about 100 kilometers. This is alsothe distance that Fibre Channel data can be transmitted on a single-mode 9-mm fiber at 1 Gb/swith long-distance SFPs.Congestion delays on the interconnect is another source of replication latency. For example, a4-KB write packet routed onto an IP link operating at 44 Mb/s (T3) incurs approximately 1millisecond in latency as the fiber channel packets are serialized onto the slower link. A burst of10 writes means the last write queued to the IP link experiences a 10-millisecond delay as it waitsfor the previous 9 writes to be transmitted. This sample congestion delay also consumes 50% of a

Choosing the intersite link 19

20-millisecond average response time budget for latency sensitive applications such as MicrosoftExchange.

Sizing bandwidth for asynchronous replicationHP P6000 Continuous Access includes an enhanced buffering technique for asynchronous replicationsolutions that utilizes the DR group write history log. This disk-based journaling insulates applicationusers from latency delays caused by propagation delays and intermittent congestion on the link.However, enhanced asynchronous replication can leave user data can be at risk from a site disaster.The capacity of the link to move data from the log file determines the amount of exposure.Establishing an optimal balance between the cost of bandwidth and the value of the data beingprotected requires an accurate sizing.It may appear that sizing link capacity equal to the average write byte rate is optimal. After all,whatever data goes into the log must be replicated. However, there are several problems in usingaverages. The primary issue is that averaging fails to take into account the tolerance to data lossas specified in the RPO. The second is a practical matter when computing averages. What timeinterval is meaningful for the averaging? While it may be convenient to look at the average changerate because this information is often readily available, using averages will usually lead to asub-optimal or undersized bandwidth capacity.

Evaluating bandwidth capacityCompare the average load and peak write rate of your applications with the capacity of intersitelink technologies and determine which technology is most effective. With XCS 6.000 and later,the maximum capacity measure is averaged over the RPO interval. This limitation allows I/O froma failed link or fabric to run on the active link or fabric without additional failures caused byoverloading the surviving fabric.You can use the Data Replication Designer to analyze bandwidth data. The Data ReplicationDesigner is supported on Windows only. See “Tools for gathering SAN data” (page 14) for moreinformation on Data Replication Designer and other tools available for evaluating bandwidth.

Choosing a write modeYou specify the replication write mode when you create DR groups. The choice of write mode,which is a business decision, has implications for bandwidth requirements and RPO. Synchronousmode provides greater data currency because RPO will be zero. Asynchronous mode providesfaster response to server I/O, but at the risk of losing data queued at the source side if a sitedisaster occurs. Asynchronous write mode can be basic or enhanced, depending on the softwareversion of the controller.The write mode selection has implications for the bandwidth required for the intersite link. In general,synchronous mode (and shorter RPOs) requires higher bandwidth and smaller network latencies.For instance, synchronous mode can require twice the bandwidth during average workloads andten times the bandwidth during peak loads.For complete information on which write modes are supported on each version of controller software,see the HP P6000 Enterprise Virtual Array Compatibility Reference. For more information aboutRPO, see “Recovery point objective” (page 18).


NOTE:• A request to convert from synchronous mode to asynchronous mode is executed immediately.

A request to convert from asynchronous mode to synchronous mode is executed after the datain the DR group write history log or the I/Os in the write pending queue are merged to thedestination array.

• During the conversion from enhanced asynchronous mode to synchronous mode, an I/Othrottling mechanism allows one new write to a DR group for every two DR group write historylog entry merges.

Asynchronous write modeIn asynchronous write mode, the source array acknowledges I/O completion after the data ismirrored across both controllers on the source array. Asynchronous replication prioritizes responsetime over data currency.The asynchronous replication sequence depends on the version of controller software running onthe arrays. For more information, see the HP P6000 Enterprise Virtual Array Compatibility Reference.XCS 10000000 supports the selection of either basic asynchronous mode or enhanced asynchronousmode. The asynchronous write mode behavior for both basic and enhanced is unchanged fromearlier controller software. The user selectable asynchronous functionality is available only whenboth the local and remote arrays are running XCS 10000000 or later.

Basic asynchronous modeThe basic asynchronous sequence is as follows:1. A source array controller receives data from a host and stores it in cache.2. The source array controller acknowledges I/O completion to the host.3. The source array controller sends the data to the destination array controller.4. The destination controller stores the data in cache.5. The destination array controller mirrors data in its write cache and acknowledges I/O

completion to the source controller.6. When the source array receives the acknowledgment from the target array, it removes the

data from the write history log.The maximum size of the write pending queue limits asynchronous performance. VCS 3.xxx supports64 outstanding host writes. All other VCS versions support 128 outstanding host writes. With asmall write pending queue, lower bandwidths struggle to support applications with erratic or highpeak load rates.

Enhanced asynchronous modeXCS 6.xxx and later supports an enhanced asynchronous write mode, which uses the write historylog for the DR group as a place to hold I/Os waiting to be replicated to the remote array. Youcan select the size of the log file up to a maximum of 2 TB.

NOTE: Enhanced asynchronous mode requires XCS 6.xxx or later on both arrays.

The enhanced asynchronous write sequence is as follows:1. A source array controller receives data from a host and stores it in the cache of the local LUN

and the write history log cache.2. The source array controller acknowledges I/O completion to the host.3. The source controller takes data from the write history log and sends the data to the remote

array.4. The destination array controller stores the data in cache and acknowledges I/O completion

to the source controller.

Choosing a write mode 21

5. When the source array receives the acknowledgment from the target array, it removes thedata from the write history log.

Synchronous modeIn synchronous write mode, the source array acknowledges I/O completion after replicating thedata on the destination array. Synchronous replication prioritizes data currency over responsetime.1. A source array controller receives data from a host and stores it in cache.2. The source array controller replicates the data to the destination array controller.3. The destination array controller stores the data in cache and acknowledges I/O completion

to the source controller.4. The source array controller acknowledges I/O completion to the host.Synchronous replication has no need for a write pending queue.

Maintaining DR group I/O consistencyHP P6000 Continuous Access maintains write order across all members of the DR group. This isdone by adding a DR group-specific sequence number to each write as the data is replicated fromthe source array to the destination array. Before processing a write, the destination array verifiesthat it was received in the correct order. If any write is received out of order, processing for allwrites to any member of the DR group stops. Once write order is re-established, the processingcontinues.

NOTE: If the write history log overflows for any reason, an out-of-order normalization occurs toresynchronize the DR group. The destination virtual disks will be I/O inconsistent until normalizationcompletes.


3 Planning the remote replication fabricThis chapter describes the supported HP P6000 Continuous Access configurations.

Basic dual-fabric configurationFigure 5 (page 23) shows the basic HP P6000 Continuous Access configuration with Fibre Channellinks. Hosts (5) have two HBAs, one connected to the blue fabric (6) and the other connected to aredundant gold fabric (8). Arrays have two controllers, each connected to both fabrics for a totalof four connections. (For configurations with more than two ports per controller, see “Advancedconfigurations” (page 29). Local and remote fabrics are connected by intersite links (7 and 9).

Figure 5 Basic configuration over fiber

6. Host I/O and replication fabric—blue1. Data center 1

7. Intersite link—blue2. Data center 2

8. Host I/O and replication fabric—gold3. LAN connection

9. Intersite link—gold4. Management server

10. Dual-controller arrays5. Hosts

This configuration provides no SPOF at the fabric level. If broken cables, switch updates, or anerror in switch zoning cause one fabric to fail, the other fabric can temporarily carry the entireworkload.

Basic configuration limitsFor fabric rules and size limits, see Part II of the HP SAN Design Reference Guide. Limits apply tothe combined local-remote fabric in HP P6000 Continuous Access configurations.The number of supported arrays and hosts in an HP P6000 Continuous Access configurationdepends on the array. This information is available in Part III of the HP SAN Design ReferenceGuide.

Basic dual-fabric configuration 23

You can use switches to create zones and work around some fabric limitations. For example:

• Unsupported hosts and incompatible arrays can be on a fabric with HP P6000 ContinuousAccess if they are in independent zones. For compatibility with operating systems and othersoftware, see the HP P6000 Enterprise Virtual Array Compatibility Reference.

• A fabric can include multiple HP P6000 Continuous Access solutions.For more information about zoning, see “Creating fabrics and zones” (page 58).

Basic configuration rulesThe following rules apply to the basic HP P6000 Continuous Access configuration:

• Each array must have dual array controllers.

• Host operating systems should implement native or installed multipath software. For compatiblemultipath solutions, see the HP P6000 Enterprise Virtual Array Compatibility Reference.

• Local and remote arrays must be running compatible controller software. For information aboutsupported replication relationships between arrays with VCS and XCS controller software,see the HP P6000 Enterprise Virtual Array Compatibility Reference.

• A minimum of two HBAs (or one dual-port HBA) is recommended for each host to ensure noSPOF between the host and the array. For maximum HBA ports, see the HP SAN DesignReference Guide.

• All virtual disks used by a single application must be in a single DR group; only one applicationper DR group is recommended.

• All members of a DR group will be assigned to the same array controller.

• Each site must have at least one management server. Two management servers arerecommended for high availability after a disaster.

• It is highly recommended that you use dedicated HP P6000 Command View managementservers with HP P6000 Continuous Access. Although you can install HP P6000 CommandView on an application server that is accessing the array, care should be taken if you decideto do so. If LUN presentation is not managed properly, a shared HP P6000 Command Viewmanagement/application server may have access to LUNs on both the source array and thedestination array. This is undesirable and could result in two servers simultaneously performingI/O to a common LUN, resulting in an undesirable data state.

In addition, copies of HP P6000 Continuous Access and array/operating system supportdocumentation should be accessible at each site. The documentation facilitates disaster recovery,rebuilding, or repair of the surviving system if access to the other site is lost.

Extended fabric using long-distance GBICs and SFPsAdding long-distance and very-long-distance GBICs and SFPs to simple Fibre Channel links increasesthe possible distance between sites. For more information about the use of long-distance fiber andsupported GBICs and SFPs, see the HP SAN Design Reference Guide.

Extended fabric using WDMAdding dense or coarse WDM to basic Fibre Channel allows greater distances between sites thanlong-distance GBICs and SFPs. The difference between WDM and basic fiber configurations is theaddition of a multiplex unit on both sides of the intersite link.

24 Planning the remote replication fabric

When using WDM, consider the following:

• WDM installation must conform to vendor specifications.

• Performance is affected by extreme distance and/or limited buffer-to-buffer credits on the FibreChannel switch.

• Some switch vendors may limit the maximum distance between sites.Additional configuration rules apply to WDM configurations:

• Connecting the switch to the WDM unit typically requires one switch-to-WDM interface cableper wavelength of multimode fiber.

• Switches may require an Extended Fabric license.For more information about using WDM with fiber, see the HP SAN Design Reference Guide.

Fabric to IPExtended fabrics convert Fibre Channel to IP to maximize the separation distance.

NOTE: Many solutions include dual fabrics between data centers to ensure there is no SPOF inthe event of a fabric failure, but redundant fabrics are not required to run HP P6000 ContinuousAccess. Some best practice cabling solutions, such as the five-fabric configuration, do not supportdual-fabric solutions. See “Five-fabric configuration” (page 29).

Fibre Channel-to-IPThe remote replication configuration over IP is similar to the basic remote replication configurationover fiber with the addition of Fibre Channel-to-IP (FC-to-IP) gateways. Dual fabrics require twodedicated gateways at each site, one per fabric for a total of four per solution, to eliminate SPOFs.See Figure 10 (page 31) and Figure 12 (page 34). For a current list of supported gateways andnetwork specifications, see the HP SAN Design Reference Guide.

FC-to-IP configuration limitsRemote replication over IP has the same configuration limits as described in “Basic configurationlimits” (page 23). Multiple instances can share the fabric if the network bandwidth is sufficient forall traffic flowing between sites in a worst-case scenario.In addition, some gateways do not support combining the data from two FC ports into one IP port.For details, see the HP SAN Design Reference Guide and vendor documentation.For information about different requirements for single intersite (interswitch) links versus shared ordual intersite (interswitch) links, see the HP SAN Design Reference Guide.

FC-to-IP configuration rulesIn addition to the “Basic configuration rules” (page 24), consider the following specific requirementsfor IP configurations:

• Some FC-to-IP gateways are supported only on older B-series switches and require the RemoteSwitch Key (vendor-dependent).

• For gateways requiring the Remote Switch Key, and on switches where the Remote SwitchKey is installed, do not enable suppression of F-Class frames. Doing so limits the supportedconfiguration to one switch per fabric at each site. See the HP SAN Design Reference Guidefor more information.

• The FC-to-IP gateways should be same model and software version on each side of the IPnetwork in the fabric.

• The first Fibre Channel switch at each end of an FC-to-IP gateway (the first hop) should besame model and software version. This avoids interoperability issues because the MPX willmerge the fabrics.

Fabric to IP 25

Contact a third-party vendor to acquire and install all SMF optic cables, any MMF optic cableslonger than 50 meters, and the FC-to-IP interface boxes.

Configurations with application failoverThe configurations in this section include host software that works with HP P6000 ContinuousAccess to provide application and data failover capability.

HP Cluster ExtensionHP Cluster Extension offers protection against application downtime due to a fault, failure, or sitedisaster by extending a local cluster between data centers over metropolitan distance. HP ClusterExtension reinstates critical applications at a remote site within minutes of an adverse event,integrating your open-system clustering software and HP P6000 Continuous Access to automatefailover and failback between sites. This dual integration enables the cluster software to verify thestatus of the storage and the server cluster. The cluster software can then make correct failover andfailback decisions, thus minimizing downtime and accelerating recovery.For more information, download the HP Cluster Extension documentation from the Manuals pageof the HP Business Support Center website:http://www.hp.com/support/manualsIn the Storage section, click Storage Software and then select HP Cluster Extension Software in theStorage Replication Software section.The HP P6000 Continuous Access links must have redundant, separately routed links for eachfabric. The cluster network must have redundant, separately routed links. Cluster networks and HPP6000 Continuous Access can share the same links if the link technology is protocol-independent(for example, WDM) or if the Fibre Channel protocol is transformed to IP. Figure 6 (page 26)shows an example of a cluster configuration.

NOTE: Most of the configurations shown in this guide will work with HP Cluster Extension providedthe configuration used meets all HP Cluster Extension and any underlying cluster softwarerequirements.

Figure 6 HP Cluster Extension configuration

7. Intersite link—blue fabric1. Data center 1

8. Host I/O and replication fabric—gold2. Data center 2

9. Intersite link—gold fabric3. LAN connection


http://www.hp.com/support/manuals

10. Dual-controller arrays4. Management server

11. Cluster site5. Hosts

6. Host I/O and replication fabric—blue

HP Metrocluster Continuous AccessHP P6000 Continuous Access supports a ServiceGuard cluster running on HP-UX 11i v1 or HP-UX11i v2 Update 2. Also known as HP-UX Metrocluster Continuous Access, this configuration hashalf the cluster in each of two data centers and uses HP P6000 Continuous Access to replicatedata between the data centers. In the event of a fault, failure, or disaster, HP-UX MetroclusterContinuous Access automatically reconfigures the destination DR group. This allows automaticfailover of ServiceGuard application packages between local and remote data centers. For moreinformation about HP-UX Metrocluster Continuous Access EVA, see the HP website:http://h71028.www7.hp.com/enterprise/cache/4171-0-0-0-121.html

HP ContinentalclusterHP P6000 Continuous Access supports HP Continentalcluster on HP-UX 11i v1 and HP-UX 11i v2Update 2 that is spread across separate data centers at unlimited distances.In this configuration, HP P6000 Continuous Access is used to replicate data from one site (wherethe primary cluster resides) to the other site (where the recovery cluster resides). Upon primarycluster failure, HP Continentalcluster fails over the ServiceGuard application packages from theprimary cluster to the recovery cluster.

Reduced-availability configurationsIMPORTANT: The following reduced-availability configurations are not recommended forproduction environments.

The following configurations are supported primarily to reduce the cost of test and developmentconfigurations. They are not recommended for production environments. Because they have oneor more SPOFs, they do not offer the same level of disaster tolerance and/or high availability asdescribed in “Basic dual-fabric configuration” (page 23).

Single-fabric configurationThe single-fabric HP P6000 Continuous Access solution is designed for small, entry-level tests orproof-of-concept demonstrations where some distance is needed between each of the two switchesin the solution. This solution can also be used for producing copies of data needed for datamigration or data mining, but is not recommended for ongoing production due to multiple SPOFs.Fabric zoning is required to isolate hosts, as documented in the HP SAN Design Reference Guide.The two switches share one intersite link, leaving the remaining ports for hosts, array controllers,and a management server. For example, if a 16-port switch is being used, the remaining 15 portssupport up to:

• Four hosts, one array, and one management server

• Two hosts, two arrays, and one management serverFigure 7 (page 28) shows a single-fabric configuration. Any supported fabric topology describedin the HP SAN Design Reference Guide can be used. All intersite links supported in the basicremote replication configuration are also supported in the single-fabric configuration. This meansthat the intersite link can be direct fiber, a single WDM wavelength, or a single FCIP link.

Reduced-availability configurations 27

http://h71028.www7.hp.com/enterprise/cache/4171-0-0-0-121.html

NOTE: When creating an intersite FCIP link using B-series or C-series routers, the respective LSANand IVR functionality can provide SAN traffic routing over the FCIP connection while preventingthe merging of the two sites' fabrics in to a single fabric. LSANs and IVR enable logical fabricseparation of the two sites, ensuring that a change on one site's fabric does not affect the othersite.The HP FCIP Distance Gateways (MPX110) will allow the fabrics on both sites to merge into asingle large fabric. SAN traffic isolation can still be accomplished with the FCIP Distance Gatewaysusing SAN zoning, but this will not provide fabric separation. When using the FCIP DistanceGateways, fabric configuration changes should be made carefully, and it may be desirable todisable the ISL until all changes are complete and the fabric is stable.

Figure 7 Single-fabric configuration

5. Hosts1. Data center 1

6. Host I/O and replication fabric2. Data center 2

7. Intersite link3. LAN connection


Single-switch configurationThe single-switch HP P6000 Continuous Access configuration is designed for small, single-site,entry-level tests or proof-of-concept demonstrations. This non-disaster-tolerant solution can also beused for producing copies of data needed for data migration or data mining.A 16-port switch can support a maximum of three hosts, two arrays, and one management server.Large switches support more hosts and/or storage arrays if all HBA and array ports are connectedto the same switch. Fabric zoning is required to isolate servers as defined in HP SAN DesignReference Guide. The fabric can be any supported fabric topology described in the HP SAN DesignReference Guide.An example of the single-switch configuration is shown in Figure 8 (page 29).

NOTE: This solution can also be used for producing copies needed for data migration or datamining, but is not recommended for ongoing production due to multiple SPOFs.


Figure 8 Single-switch configuration

4. Hosts1. LAN connection

5. Dual-controller arrays2. Switch

3. Management server

In this example, two hosts might be clustered together using a supported cluster technology for theoperating system. The third host would be a single server running the same operating system asthe clustered hosts, and therefore available as a backup to the cluster. In another example, thethird host could have a different operating system and be a standalone server used for training onstorage failover.

Single-HBA configurationA host containing a single HBA can be attached to any of the following configurations:

• Basic HP P6000 Continuous Access and optional links

• Single fabric

• Single switchThis option allows the use of hosts that support only one HBA. Availability is reduced due to theSPOF in connecting the server to the array.

Advanced configurationsThe following configurations use separate controller host ports for host I/O and replication I/O.This enhances security and reduces contention between host I/O and replication I/O on a singlecontroller host port. Any HP P6000 Continuous Access configuration using FC-to-IP gateways tocommunicate with the destination site should adhere to this recommendation.

Five-fabric configurationThe five-fabric solution shown in Figure 9 (page 30) consists of one fabric (8) that is dedicated toreplication and four fabrics (blue and gold at each site) that are dedicated to I/O between hostsand arrays. Figure 10 (page 31) shows the same configuration using FC-to-IP for the replicationfabric.In the five-fabric configuration, blue and gold fabrics (6 and 7) are dedicated to host I/O. Aseparate black fabric consisting of the switches (8) and the single intersite link (9) pass all thereplication I/O. The dedicated switch (8) combines the data into one intersite link.

Advanced configurations 29

NOTE:• For more information about the connections used to implement this configuration, see “A single

physical fabric” (page 66). The five fabric configurations can be physically separate fabrics(see Figure 24 (page 62)) or a single physical fabric zoned into five logical fabrics usingswitch zoning (see Figure 27 (page 66)).

• When creating an intersite FCIP link using B-series or C-series routers, the respective LSANand IVR functionality can provide SAN traffic routing over the FCIP connection while preventingthe merging of the two sites' fabrics in to a single fabric. LSANs and IVR enable logical fabricseparation of the two sites, ensuring that a change on one site's fabric does not affect theother site.The HP FCIP Distance Gateways (MPX110) will allow the fabrics on both sites to merge intoa single large fabric. SAN traffic isolation can still be accomplished with the FCIP DistanceGateways using SAN zoning, but this will not provide fabric separation. When using the FCIPDistance Gateways, fabric configuration changes should be made carefully, and it may bedesirable to disable the ISL until all changes are complete and the fabric is stable.

• If you use FCIP, use the same model FCIP gateway at each location.

• To compensate for the SPOF in a five-fabric solution (the intersite link), HP recommends thatavailability be a QoS metric on the intersite link.


Figure 9 Five-fabric configuration

6. Host I/O fabric—blue1. Data center 1

7. Host I/O fabric—gold2. Data center 2

8. Dedicated replication fabric3. LAN connection

9. Intersite link4. Management server



Figure 10 Five-fabric configuration with FC-to-IP


8. Dedicated replication fabric2. Data center 2

9. Intersite link3. LAN connection


11. FC-to-IP5. Hosts

6. Host I/O fabric—blue


Six-fabric configurationThe six-fabric configuration shown in Figure 11 (page 33) consists of two fabrics that are dedicatedto replication and four fabrics that are dedicated to I/O between the hosts and arrays.Figure 12 (page 34) shows the same configuration using FC-to-IP for the replication fabrics.

NOTE:• For more information about the connections used to implement this configuration, see “Dual

physical fabric with six zones” (page 67). The six fabric configurations can be physicallyseparate fabrics (see Figure 25 (page 63) and Figure 26 (page 64)) or two physical fabriczoned into six logical fabrics using switch zoning (see Figure 28 (page 68) andFigure 29 (page 69)).

• When creating an intersite FCIP link using B-series or C-series routers, the respective LSANand IVR functionality can provide SAN traffic routing over the FCIP connection while preventingthe merging of the two sites' fabrics into a single fabric. LSANs and IVR enable logical fabricseparation of the two sites, ensuring that a change on one site's fabric does not affect theother site.The HP FCIP Distance Gateways (MPX110) will allow the fabrics on both sites to merge intoa single large fabric. SAN traffic isolation can still be accomplished with the FCIP DistanceGateways using SAN zoning, but this will not provide fabric separation. When using the FCIPDistance Gateways, fabric configuration changes should be made carefully, and it may bedesirable to disable the ISL until all changes are complete and the fabric is stable.

• In a six-fabric configuration, each HP P6000 Continuous Access relationship must include atleast one eight-port controller pair.


• If you use FCIP, use the same model FCIP gateway at each location.

In this example, four local and remote fabrics (6 and 7 at each site) are dedicated to host I/O. Atthe same time, there are separate redundant fabrics made up of switches (8 and 10) and twointersite links (9 and 11).


Figure 11 Six-fabric configuration


8. Dedicated replication fabric—gold2. Data center 2

9. Intersite link—gold fabric3. LAN connection

10. Dedicated replication fabric—blue4. Management server

11. Intersite link—blue fabric5. Hosts

12. Dual-controller arrays6. Host I/O fabric—blue


Figure 12 Six-fabric configuration with FC-to-IP

8. Dedicated replication fabric—gold1. Data center 1

9. Intersite link—gold fabric2. Data center 2

10. Dedicated replication fabric—blue3. LAN connection

11. Intersite link—blue fabric4. Management server


13. FC-to-IP—gold replication fabric6. Host I/O fabric—blue

14. FC-to-IP—blue replication fabric7. Host I/O fabric—gold


4 Planning the array configurationThis chapter provides an overview of factors to consider when planning an array configuration forremote replication.Many remote replication features depend on the array controller software. For more informationabout planning, see the HP Enterprise Virtual Array Configuration Best Practices White Paper foryour array model.

Planning disk groupsPlanning the necessary disk groups to meet your I/O requirements should be done when configuringthe array. See the HP Enterprise Virtual Array Configuration Best Practices White Paper forrecommendations on configuring the array properly.When data is replicated remotely, application performance is not necessarily improved by increasingthe number of disks in a disk group because response time for application writes includes the timefor replication. In addition, sequential access (read or write) is limited by the per-disk performancerather than by the number of disks in the disk group. In synchronous mode, performance will likelybe limited by replication before it is limited by the number of disks. When using enhancedasynchronous write mode, DR group logging will impact the write workload imposed on the array.

Determining the number of disk groupsTo determine if the default disk group will meet your remote replication needs, consider the following:

• Separate disk groups can help ensure that data is recoverable if a disk group fails. However,multiple disk groups result in a slightly higher cost of ownership and potentially lowerperformance.

• In general, distributing the workload across the greatest number of disks in a single disk groupprovides the best performance.

• Disk groups must provide sufficient free space for snapshots and snapclones (if used), and forDR group write history logs.

• A DR group can contain virtual disks from multiple disk groups, but all DR group membervirtual disks must be in the same array and must be set to use the same preferred controlleron the array.

For specific guidelines on choosing the number and size of disk groups, see the HP EnterpriseVirtual Array Configuration Best Practices White Paper for your array model.

Specifying disk group propertiesUse HP P6000 Command View to initialize each local and remote array and create additionaldisk groups as needed. When configuring disk groups for remote replication, consider the following:

• Assign different names to local and remote arrays to ensure the ability to fail over DR groups.

• Select disk protection level double for disk groups that will contain DR group members. (Notethat this differs from the best practice in nonreplicating configurations.) The protection leveldetermines the capacity reserved for reconstructing disks after a disk failure. Selecting doubledisk protection reserves the largest amount of disk capacity and provides the most dataprotection.

• Calculate the disk group occupancy alarm setting according to the array best practice, andensure that you include the total maximum capacity for all DR group write history logs. Seethe HP Enterprise Virtual Array Configuration Best Practices White Paper for your array model.

Planning disk groups 35

Planning DR groupsVirtual disks that contain the data for one application must be in one DR group. For optimumfailover performance, limit the virtual disks in a DR group to as few as possible.

DR group guidelinesThe following guidelines apply for DR groups:

• Source and destination arrays must have remote replication licenses.

• The maximum number of virtual disks in a DR group and the maximum number of DR groupsper array vary with controller software versions. For current supported limits, see the HP P6000Enterprise Virtual Array Compatibility Reference.

• The array selected as the destination is specified by the administrator when setting up replicationand creating the DR group.

• All virtual disks that contain data for a common application must be in a common DR group.HP recommends one application per DR group.

• All interdependent virtual disks such as host based logical volumes must be in a common DRgroup.

• DR groups can contain members from multiple disk groups.

• DR group members can exist in any supported redundancy (Vraid) level.

• DR groups that include FATA drives must meet the necessary configuration requirements. Formore information on FATA drives, see “DR groups with FATA or SAS Midline drives” (page 38).

• All members of a DR group have a common preferred controller. Virtual disks added to a DRgroup will take on the presentation and failover status of the first virtual disk that was addedto the disk group. The preferred mode setting is failover/failback.

• With some versions of controller software, virtual disks cannot be added to or deleted froma DR group when operating in enhanced asynchronous or basic asynchronous write mode.You must change the DR group to synchronous write mode and wait for the write history logor the write pending queue to drain before you can add or remove members. This restrictionis controller software version dependent. To determine if your array has this restriction, seethe HP P6000 Enterprise Virtual Array Compatibility Reference.

• Failover is permitted only from the destination array.

• When failsafe mode is enabled, a DR group cannot be suspended.

• A suspended DR group cannot be failed over and its members cannot be removed. Exception:if ISLs are broken, a suspended DR group can be failed over.

• A DR group cannot be deleted if a member of the DR group is presented on the destinationarray.

• LUN shrink of virtual disks in a DR group is not supported for any VCS or XCS controllersoftware versions. See the HP P6000 Enterprise Virtual Array Compatibility Reference todetermine if your array supports this feature. LUN expansion is not supported on VCS 3.xxx.

• A DR group can be failed over or deleted while it is normalizing in controller software version0952x000 or later.

• Some versions of controller software support auto suspend when a full copy of the DR groupis required. This feature can be used to protect the data at the destination site by delaying thefull copy operation until a snapshot or snapclone of the data has been made. See the HPP6000 Enterprise Virtual Array Compatibility Reference to determine if your array supportsthis feature.

36 Planning the array configuration

To be added to a DR group, a virtual disk:• Cannot be a member of another DR group

• Cannot be a snapshot

• Cannot be a mirrorclone

• Must be in a normal operational state

• Must use mirrored cache

CAUTION: Before replicating a Vraid0 source Vdisk or creating a Vraid0 remote copy, considerthe limitations of Vraid0. Although Vraid0 offers the most compact storage of your data, it carriesno data redundancy. If you select a Vraid0 source Vdisk, the failure of a single drive in its diskgroup will cause the complete loss of its Vraid0 data, and replication from it will stop. If you chooseto create a Vraid0 destination Vdisk, the failure of a single drive in its disk group will cause thecomplete loss of its Vraid0 data, and replication to it will stop.

Implicit LUN transition and HP P6000 Continuous AccessImplicit LUN transition automatically transfers management of a virtual disk to the array controllerreceiving the most read requests for that virtual disk. This feature improves performance by reducingthe overhead incurred when servicing read I/Os on the non-managing controller. Implicit LUNtransition is enabled in VCS 4.xxx and all versions of XCS.When creating a virtual disk, one of the array controllers is selected for managing the virtual disk.Only the managing controller can issue I/Os to a virtual disk in response to host read and writerequests. If a read I/O request arrives on the non-managing controller, the read request must betransferred to the managing controller for servicing. The managing controller issues the I/O request,caches the read data, and mirrors that data to the cache on the non-managing controller, whichthen transfers the read data to the host. Because this type of transaction, referred to as a proxyread, requires additional overhead, it provides less than optimal performance. (There is little impacton a write request as all writes are mirrored in both controllers’ caches for fault protection.)With implicit LUN transition, if the array detects that a majority of read requests for a virtual diskare proxy reads, management of the virtual disk will be transitioned to the non-managing controller.This improves performance by making the controller that is receiving most of the read requests themanaging controller, which reduces the proxy read overhead for subsequent I/Os.On XCS 6.100 and later, implicit LUN transition is disabled for all members of an HP P6000Continuous Access DR group. Because HP P6000 Continuous Access requires that all members ofa DR group be managed by the same controller, it would be necessary to move all members ofthe DR group if excessive proxy reads were detected on any virtual disk in the group. This wouldimpact performance and create a proxy read situation for the other virtual disks in the DR group.Not implementing implicit LUN transition on a DR group does create the possibility that a virtualdisk in the DR group may be experiencing excessive proxy reads.

DR group name guidelineHP recommends that you assign unique names to DR groups. Duplicate names are supported forDR groups on different arrays, but they are not supported for DR groups on the same array. DRgroup names are case sensitive in HP P6000 Command View but are not case sensitive in HPP6000 Replication Solutions Manager. In rare cases, this can lead to issues in HP P6000 ReplicationSolutions Manager. For example, if you use HP P6000 Command View to create two DR groups,DRgroupA and drgroupa on the same array, there will be no problem in HP P6000 CommandView; however, actions and jobs in HP P6000 Replication Solutions Manager involving either ofthese DR groups may fail or result in unexpected behavior.

Planning DR groups 37

Increasing the size of the write history log file in enhanced or basic asynchronous modeYou can expand the size of a DR group member (virtual disk) whether the DR group is in synchronousor asynchronous mode. However, when you expand the size of a virtual disk in a DR groupoperating in enhanced asynchronous or basic asynchronous mode, the write history log file sizedoes not increase. See the HP P6000 Enterprise Virtual Array Compatibility Reference.To increase the log file size in enhanced asynchronous mode, you must first set the DR group tosynchronous mode as follows:

NOTE: The following procedure requires you to temporarily change the write mode of the DRgroup to synchronous. While host I/O is being replicated synchronously, server performance willbe negatively impacted.

1. Change the write mode from asynchronous to synchronous.2. Allow the write history log to drain.3. Increase the size of the log.4. Change the write mode back to asynchronous.

DR groups with FATA or SAS Midline drivesHP P6000 Continuous Access supports the use of FATA or SAS Midline drives on an array. However,you must ensure that I/O activity to the source array DR group members does not exceed thereduced duty cycle requirements for FATA or SAS Midline drives.Before using FATA or SAS Midline drives in an HP P6000 Continuous Access environment, considerthe following factors:

• FATA drive duty cycle—FATA or SAS Midline drives have a significantly reduced duty cyclerelative to Fibre Channel drives.

• Write I/O rate on the source array— Evaluate the level of write activity to the DR group.

• Type of write I/Os (sequential or random)—Evaluate the type of write I/O to the DR group.When using FATA or SAS Midline drives on the destination array, you must ensure that the driveduty cycle will not be exceeded if a DR group failover occurs. In the event of a failover, write andread I/O is directed to the new source (previously the destination) DR group members. If the readand write rates and types of writes to the source array do not meet the reduced duty cyclerequirements of the FATA drives, the drives should not be used for DR group destination virtualdisks.

IMPORTANT:• If your environment requires higher performance and reliability, you may want to consider

using Fibre Channel drives rather than FATA drives for the destination array DR group. Thiswill ensure a consistent level of operation in the event of a failover.

• When using FATA drives, make sure they have the latest drive firmware installed.

Planning the data replication protocolFibre Channel switches typically offer two types of frame routing between nPorts:

• Source ID/Destination ID (SID/DID) routing—Routes all exchanges between a port pair throughthe fabric using the same path through the fabric.

• Exchange-based routing—Transfers all frames within a SCSI exchange using the same path.Other SCSI exchanges can use alternate paths.


NOTE: With HP B-series switches the SID/DID protocol is known as Port-based routing; with HPC-series switches the SID/DID protocol is known as Flow based load balancing. Both B-series andC-series switches use exchange-based routing terminology for SID/DID and originator exchangeID (OXID) routing.

The original replication protocol used with HP P6000 Continuous Access is HP FC Data ReplicationProtocol (HP-FC). This protocol uses multiple exchanges for each data replication transfer. One ormore exchanges are used to transfer data, and an additional exchange is used for commandinformation. HP-FC requires that all frames in the transfer be delivered in order using the samepath even if they are for different exchanges. Therefore, if HP-FC is enabled, the fabric must useSID/DID routing.The new HP SCSI FC Compliant Data Replication Protocol (HP SCSI-FCP) is a full SCSI protocolimplementation and can take advantage of the exchange-based routing available in fabric switches.Replication data transfer SCSI exchanges can use alternate paths.HP SCSI-FCP and HP-FC protocols are supported on controller software versions 0953xxxx or later;earlier versions of the controller software support HP-FC only. The successful creation of DR groupsrequires that both the source and destination arrays be configured for compatible replicationprotocols.

NOTE: H-series FC switches are only supported with XCS 09534000 or later and the HP SCSI-FCPprotocol. For the latest information about supported firmware, see the P6000/EVA Array Streamsand the H-series FC Switch Connectivity Stream on the HP Single Point of Connectivity Knowledge(SPOCK) website at http://www.hp.com/storage/spock.You must sign up for an HP Passport to enable access.

Selecting the data replication protocolWhen selecting the data replication protocol for the array, three options are available. The threeavailable options are shown in “Data replication protocol selection” (page 40). The option currentlybeing used is indicated by the option selected.

• HP FC Data Replication Protocol (HP-FC)—Choosing this option requires that all transfers becompleted in order, which is accomplished by the proper configuration of the SAN fabricswitches for SID/DID. For more information on the required switch settings, see “VerifyingFibre Channel switch configuration” (page 51).

NOTE: HP-FC protocol should not be used with a SAN configured for exchange-basedrouting.

An array configured for HP-FC will successfully create a DR group only with another arrayusing HP-FC. HP-FC is the default protocol for controller software versions prior to XCS0953xxxx and can be selected as a protocol in later versions. Use of HP-FC with improperfabric configuration will result in significant performance degradation.

• HP SCSI FC Compliant Data Replication Protocol (HP SCSI-FCP)—Choosing this option supportsthe transfer of data replication traffic in a fabric configured for exchange-based (SID/DIDOXID) routing. This protocol takes advantage of the exchange-based fabric setting, but is notdependent on the fabric setting. Exchange-based routing is not required when using thisprotocol. For more information on the required switch settings, see “Verifying Fibre Channelswitch configuration” (page 51).

• Either—Choose this option when the SAN contains arrays running both HP-FC and HP SCSI-FCPprotocols. This option enables arrays capable of HP-FC only to successfully create DR groupswith arrays running controller software version 0953xxxx or later. This facilitates the migrationof data from older arrays to newer arrays. The same fabric considerations for HP FC DataReplication Protocol also apply to the Either option.

Planning the data replication protocol 39


NOTE: An array running XCS version 09534000 or later with the protocol selection set forEither may have DR groups created with arrays configured for HP-FC or HP SCSI-FCP. However,the fabric must be set to SID/DID routing protocol only.

The three available options are shown in “Data replication protocol selection” (page 40). Thewindow indicates the protocol currently selected.The following guidelines apply when selecting the replication protocol for each indicated task:

• Installing a new array—When initializing a new array with controller software version09534000 or later installed, the replication protocol defaults to HP SCSI-FCP. The protocolcan be changed to HP-FC if necessary.

• Upgrading an array—When upgrading an array to 09534000 or later from an earlier versionthat does not support HP SCSI-FCP, the replication protocol remains at HP-FC regardless ofwhether DR groups are present or not.

• Downgrading an array—When downgrading an array from controller software version09534000 or later to an earlier version that does not support HP SCSI-FCP, you must configurethe fabric for SID/DID then change the data replication protocol to HP FC before downgrading.These configuration changes must be completed prior to downgrading the array and bringingthe DR groups back online. When changing the protocol, data replication will stop until botharrays in the HP P6000 Continuous Access relationship are set to a compatible protocol.

Figure 13 Data replication protocol selection

Data replication protocol performance considerationsThe HP-FC modified SCSI protocol replicates data using a single round trip as compared to thetwo round trips used by the standard SCSI protocol. HP SCSI-FCP follows the standard SCSIprotocol, requiring two round trips to complete a data transfer. The following considerations canminimize the additional link overhead introduced by the dual round trip required by HP SCSI-FCP.

NOTE:• The term IP acceleration is used here to collectively refer to the Brocade FCIP FastWrite feature

and the Cisco FCIP Write Acceleration feature.• IP acceleration can only be used if the replication network between two arrays is using the

HP SCSI-FCP protocol. IP acceleration MUST NOT be enabled when using the HP-FC protocol.

The following information assumes that in both single-network and dual-network link environmentseach individual network link is capable of maintaining the solution’s defined RPO. If this is not thecase, each network link is considered a SPOF because the failure of one network link prevents thesolution from meeting its defined RPO. If each network link cannot maintain the solution’s definedRPO, you must not enable the IP acceleration feature of the Brocade or Cisco FC-IP routers. It is


also assumed that the packet loss and network latency jitter on the networks falls within HP’s definedacceptable range for HP P6000 Continuous Access replication.

• HP currently supports three FCIP router families: B-series, C-series, and HP IP Distance Gateway.The FCIP configuration can have either single or dual long-distance network links between thelocal and remote gateways. Both the Brocade and the Cisco FC-IP routers support IPacceleration, which optimizes the SCSI protocol across the IP network by reducing the numberof round trips. The HP IP Distance Gateway does not currently support IP acceleration capability.Data compression remains supported on all of these products. For detailed information onFCIP router support, see the HP SAN Design Reference Guide.

• In a single long-distance IP network link solution, consider enabling the FCIP router IPacceleration capability to optimize the SCSI protocol on the IP network.

• If IP acceleration is not enabled in a dual network environment, the FCIP router load-balancesI/O equally across the two links. If IP acceleration is enabled in a dual network environment,both the Brocade and Cisco FCIP routers will force all replication traffic to use a single networkpath, even if redundant long-distance IP networks are available. This behavior is characteristicof these routers and cannot be changed.

• In a redundant replication network solution, consider enabling IP acceleration only if bothlinks are capable of independently meeting the solution’s required RPO. IP acceleration shouldnot be enabled if either one of the networks is not capable of meeting the solution’s RPO.

• When using two equivalent (QOS) redundant long distance IP networks that are independentlycapable of meeting the solution’s RPO, consider enabling IP acceleration.

• HP SCSI-FCP also allows a tunnel to use any or all of the available paths to the remotecontroller, which may improve overall performance. To enable the simultaneous use of morethan one array host port for tunnel traffic, the ports used for data replication on both the sourceand destination arrays should be set for an equivalent priority.

NOTE:

◦ These priority settings should only be applied to ports running the HP P6000 ContinuousAccess protocol.

◦ If it is necessary to change the data replication protocol setting with existing DR groups,data replication will stop until both arrays in the HP P6000 Continuous Access relationshipare set to a compatible protocol.

Tunnel thrashTunnel thrash is the frequent closing and opening of a tunnel while holding host I/O in the transition.This occurs when peer controllers can see each other, but cannot sustain replication on any path.Tunnel thrash can be caused by the following conditions:

• High volumes of packet loss

• Incorrectly configured routers

• Rerouted IP circuits

• Oversubscribed circuitsAlthough tunnel thrash is rare, if it occurs a critical event is placed in the controller event log anddisplayed in HP Command View EVA. An event will be logged for each DR group that shares theaffected tunnel.

Planning the data replication protocol 41

If tunnel thrash occurs, perform the following tasks to resolve the situation and return to normaloperation:

• Check all switches and routers to determine if there are high volumes of packet loss.

• Ensure that all switches and routers are configured correctly.

• Contact your service provider to determine if the circuit routing has been changed.

• Determine if tunnel thrash only occurs during periods of peak activity. If it does, the circuitmay be oversubscribed and you may need to increase the bandwidth.

Tunnel thrash can occur during normalization in a configuration with two separate IP paths (twofabric or six fabric). During normalization, the process may detect high latency on the link beingused but low latency on the unused link. This can cause the normalization process to switch to theunused link. This pattern can repeat itself, causing thrashing. To avoid this situation, disable onelink until the normalization is complete.

NOTE: An informational event is generated when a tunnel opens or closes. Excessive numbersof these events is an indication of tunnel thrashing, which may lead to DR group forced loggingto maintain host accessibility.

Planning for DR group write history logsThe DR group write history log is a virtual disk that stores a DR group's host write data. The log iscreated when you create the DR group. Once the log is created, it cannot be moved. You mustplan for the additional disk capacity required for each DR group write history log. For moreinformation on DR group log size, see “DR group write history log size” (page 43).

NOTE:• You must plan for the consumption of additional capacity before implementing HP P6000

Continuous Access. If insufficient capacity is encountered, the request to enable asynchronousreplication will fail. This need for sufficient capacity applies to both the source and destinationarrays.

• In all write modes, the DR group write history log is structured as Vraid1, which consumestwice the capacity requested for the log. Although Vraid1 consumes more capacity, it providesthe highest level of protection for the log content.

• A portion of the write history log is used for metadata. On the EVA3000/5000 andEVA4x00/6x00/8x00, 3.125% of the log is reserved for metadata. On the EVA4400,EVA6400/8400, and the P6300/P6500, 6.24% of the log is reserved.

Logging in synchronous or basic asynchronous modeIn synchronous mode or basic asynchronous mode, the DR group write history log stores datawhen replication to the destination DR group is stopped because the destination DR group isunavailable or suspended. This process is called logging. When replication resumes, the contentsof the log are sent to the destination virtual disks in the DR group. This process of sending I/Oscontained in the write history log to the destination array is called merging. Because the data iswritten to the destination in the order that it was written to the log, merging maintains anI/O-consistent copy of the DR group's data at the destination.

Logging in enhanced asynchronous modeIn enhanced asynchronous mode, the DR group write history log acts as a buffer and stores thedata until it can be replicated. The consumption of the additional capacity required for the logshould not be viewed as missing capacity—it is capacity used to create the log.If necessary, you can reclaim allocated log disk space from a DR group in enhanced asynchronousmode. You must first change the write mode to synchronous and then use the log control feature


to reduce the log size. When the log content has been drained, you can return the DR group toenhanced asynchronous mode. Until the DR group is returned to enhanced asynchronous mode,the DR group operates in synchronous mode, which may impact performance.Allocated log file space is not decreased when DR group members are removed. Log space usagewill increase when members are being added to an existing DR group unless the size of the logdisk has reached the maximum of 2 TB or has been fixed to a user-defined value. For the defaultmaximum size, see the HP P6000 Enterprise Virtual Array Compatibility Reference.

NOTE:• For XCS 6.0xx and 6.1xx, asynchronous replication mode is not available during the creation

of a DR group. When creating a DR group in either of these versions of XCS, you must waitfor the completion of the initial normalization to change the replication mode to asynchronous.

• For XCS 6.200 or later that are managed using HP P6000 Command View versions 8.0.1or later, the creation of DR groups in asynchronous mode is allowed. These combinations ofXCS controller software and management software enable the addition or removal of DRgroup members while in asynchronous replication mode. See the HP P6000 Enterprise VirtualArray Compatibility Reference for details.

NormalizationThe method of synchronizing source and destination virtual disks is called normalization. Anormalization can occur whenever the source and destination array need to be brought back intosynchronization. When a DR group is first created, a normalization occurs. If a DR group writehistory log overflows, a normalization occurs to bring the source and destination arrays back intosynchronization.When a DR group is first created, a full copy normalization occurs to copy all the data in the DRgroup from the source array to the destination array, bringing the two arrays into synchronization.A normalization can also occur if the write history log used by a DR group overflows or is invalidatedby the storage administrator. Normalizations copy data from the source array to the destinationarray in 128 KB blocks. When a write history log overflows, the controller invalidates the logcontents and marks the DR group for normalization. In some cases, normalization will be optimizedto copy only blocks that were written before the write history log overflowed; not all the data inthe DR group.

DR group write history log sizeYou can set the maximum size for the DR group write history log while in synchronous mode. Theminimum size of the log depends on the replication mode. The default maximum value for the logwill differ for each replication mode, and is based on the controller software version. For detailson maximum and default log sizes, see the HP P6000 Enterprise Virtual Array CompatibilityReference.

NOTE: If you are using XCS 6.000 or later and you choose enhanced asynchronous mode, thesame amount of space must be available for the DR group write history log at both the source anddestination sites when specifying the maximum log size.

XCS 6.000 and higher you can specify the size of the DR group write history log. It is importantto ensure that the write history log is large enough that, under normal operating circumstances, itwill not overflow and result in an unexpected normalization.For XCS 6.2xx, and 09003000 or later, space for the log can be de-allocated by converting theDR group to synchronous mode, waiting for the write history log to drain, and then specifying thenew size. Adding or removing members can be done in either synchronous or asynchronous modeof operation.

Planning for DR group write history logs 43

Write history log size in synchronous or basic asynchronous modeWhen using synchronous mode or basic asynchronous mode, if logging occurs because replicationhas been suspended or the replication links have failed, the size of the log file expands in proportionto the amount of writes. The size of the log file can increase only up to the user-specified maximumvalue or to the controller's software default maximum value. The size of the log can't be changedwhile in basic asynchronous mode. You must change the write mode to synchronous, change thelog file size, and then return to basic asynchronous mode.In synchronous mode and basic asynchronous mode, the log grows as needed when the DR groupis logging and it shrinks as entries in the log are merged to the remote array. The controller considersthe log disk full when one of the following occurs:

• No free space remains in the disk group that contains the log disk.

• The log disk reaches 2 TB of Vraid1 space.

• The log reaches the default or user-specified maximum log disk size.

Write history log file size in enhanced asynchronous modeThe DR group write history log file size is set when you transition the DR group to enhancedasynchronous mode. The space for the DR group write history log must be available on both thesource and destination arrays before the DR group is transitioned to enhanced asynchronous mode.Once set, the space is reserved for the DR group write history log and cannot be reduced in sizewithout first transitioning to synchronous mode and allowing the log to drain. Note that runningin synchronous mode will probably have a large impact on server write I/O response times.For known link outage periods, the size of the log required is directly related to the length of timethe link is down and the data generation rate. For planned periods of link down time, you cancalculate the log size required. Any write history log sizing done in anticipation of planned orunplanned link outages will be in addition to the sizing done to ensure the log doesn't overflowduring normal operation.

Incorrect error message for minimum asynchronous replication log sizeIf you change the write mode of a DR group to enhanced asynchronous (between arrays runningXCS 6.0xx or later), you may see the following error message: Invalid user defined logsize.If this occurs, check the size of the log. The log size must be a minimum of 1624 MB before youcan change the mode to enhanced asynchronous replication.

Log size displayed incorrectly when creating DR groups in a mixed controller software environmentWhen creating a DR group in an environment that includes arrays running different versions ofcontroller software, the requested and actual log size for the DR group may not match. This is dueto the mixed controller software environment, and also to the limited available space for the log.This is a HP P6000 Command View display issue only and does not indicate a problem with theDR group, which will function normally.

DR group write history log locationThe array controller software chooses a default location for the DR group write history log if oneis not specified. The type of disks (online or near-online) used as the default location are determinedby the version of controller software. If you want to override the default, you can specify the locationof DR group. Table 4 (page 46) identifies the default process for selecting a disk group for the log.Once the log is created, it cannot be moved.Most arrays allow you to create DR group write history logs using economical near-online disks.If the DR pair includes an array running VCS 3.xxx, the DR group write history log is automaticallycreated using a near-online disk group if one is available when the DR group is created. If thearray is running VCS 4.xxx, XCS 6.xxx, or XCS 09xxxxxx or later, you can override the automatic


log group assignment and specify the location of the log when you create the DR group. Forversion-specific features, see the HP P6000 Enterprise Virtual Array Compatibility Reference.

IMPORTANT: When using XCS 6.000 or later, create the DR group write history log using onlineFibre Channel disks, not near-online disks. Constant writes to the DR group write history log inenhanced asynchronous mode significantly shorten the expected lifetime of near-online disks. Usingonline disks for the DR log also improves I/O performance. When using XCS 09003000 or later,select online disks for the DR group write history log by default. The ability to specify DR groupwrite history log location and size is not supported with VCS 3.xxx.

Planning for DR group write history logs 45

Table 4 Default DR group write history log placement

XCS 6.000 or laterXCS 09003000 or later

VCS, XCS 6.000 or earlierArray status

Use the defined disk group.Use the defined disk group.The array contains one defined diskgroup.

Use the online disk group.Use the near-online disk group.The array contains one near-online diskgroup and one online disk group.

Use the near-online disk groupcontaining the most average free


The array contains only multiplenear-online disk groups.

space based on the number of DRspace based on the number of DRgroup logs assigned to the diskgroups.

group logs assigned to the diskgroups.

Use the online disk group containingthe most average free space based


The array contains only multiple onlinedisk groups.

on the number of DR group logsassigned to the disk groups.

on the number of DR group logsassigned to the disk groups.



The array contains one or morenear-online disk groups, and one or moreonline disk groups. on the number of DR group logsspace based on the number of DR

assigned to the disk groups. If allgroup logs assigned to the diskonline disk groups are full orgroups. If all near-online disk groupsinoperative, use a near-online diskare full or inoperative, use an onlinegroup based on the same spacecriteria.

disk group based on the same spacecriteria.

Planning replication relationshipsOne array can have replication relationships with multiple arrays. This section describes creativeways to optimize your remote replication resources.

Bidirectional replicationIn bidirectional replication, an array can have both source and destination virtual disks that willreside in separate DR groups. (One virtual disk cannot be both a source and destinationsimultaneously.) For example, one DR group can replicate data from array A to array B, andanother DR group can replicate data from array B to array A. Bidirectional replication enablesyou to use both arrays for primary storage while they provide disaster protection for another site.When using bidirectional replication: disk groups on arrays in a bidirectional relationship shouldbe appropriately sized for the load they will be carrying. Consider the bandwidth as twounidirectional flows, and add the two flows together to determine the bandwidth requirements.For other considerations related to bidirectional replication, see the HP Enterprise Virtual ArrayConfiguration Best Practices White Paper for your array model.


System fan-out replicationIn the system fan-out replication shown in Figure 14 (page 47), one DR group is replicated fromarray A to array B, and another DR group is replicated from array A to array C.

CAUTION: In a mixed array environment that includes an EVA3000/5000 array, the host portsof the fan-in target or the fan-out source should be isolated. This is necessary because anEVA3000/5000 has fewer resources to handle inter-array replication traffic. To accommodatethe reduced number of available resources on the EVA3000/5000, an EVAx100 or EVAx400array limits its resource allocation to match the lower protocol of the EVA3000/5000. This mayresult in reduced replication traffic performance between arrays normally capable of higherperformance.This situation occurs if the same host port (shared port) is used to connect to both an EVA3000/5000and an EVA4000/6000/8000, EVAx100, or EVAx400. (For information on displayingarray-to-array connection information, see “Changing host port data replication settings” (page 56).)If the shared host port configuration is temporary, after the EVA3000/5000 is removed the sharedport must be disabled and then enabled, which forces the connection to the remaining arrays toclose and reopen. This ensures that the remaining arrays use the higher level of available resourceswithin the controller software. If the shared host port configuration is not temporary, the connectionsmust use isolated host ports for EVA3000/5000 data replication connections to eliminate thepossibility of reduced replication performance. For details on creating port isolation using zoning,see “Dual-fabric replication zone fan-in/fan-out for port isolation: sheet 1” (page 91).

Figure 14 System fan-out replication

1. Array A

2. Array B

3. Array C

Planning replication relationships 47

Fan-in replicationIn the fan-in replication shown in Figure 15 (page 48), one DR group is replicated from array Ato array C, and another DR group is replicated from array B to array C.

Figure 15 Fan-in replication

1. Array A

2. Array B

3. Array C


Cascaded replicationIn cascaded replication, one DR group is replicated from array A to array B, and another DR groupis replicated from array B to array C. In this configuration, the source disk for replication from thearray B to array C is a snapclone of the destination disk in the replication from array A to arrayB. See Figure 16 (page 49). Snapclone normalization must complete on array B before the newsnapclone can be put in a new DR group.

Figure 16 Cascaded replication

1. Array A

2. Array B

3. Array C

NOTE: Using a mirrorclone instead of a snapclone to make the point-in-time copy of the destinationon array B is not supported.

Planning replication relationships 49

5 Planning the solutionThis chapter describes general design considerations for the different operating systems, applications,and storage management components that you can use when planning a remote replication solution.

Operating system considerationsThis section describes the operating systems supported in remote replication solutions. It alsodescribes the operating system capabilities that are available in an HP P6000 Continuous Accessenvironment.

NOTE: These capabilities are not always available in non–HP P6000 Continuous Accessenvironments.

Supported operating systemsThe ability for HP P6000 Continuous Access to work with an operating system is determined bythe operating system support documents posted on the SPOCK website at http://www.hp.com/storage/spockIf an operating system is supported with a particular array model and controller software version,then HP P6000 Continuous Access is supported with that operating system.

Operating system capabilitiesThis section describes two operating system capabilities that are available in an HP P6000Continuous Access solution: boot from SAN and bootless failover.

Boot from SANWith HP P6000 Continuous Access, you can replicate boot disks to a remote array and use themto recover the host and applications. Refer to the OS-specific documentation on the SPOCK websitefor operating systems that support boot from SAN and boot disk failover.

IMPORTANT: Do not use HP P6000 Continuous Access to replicate swap files.

Bootless failoverBootless failover allows destination servers to find the new source (after failover of the storage)without rebooting the server. This capability also includes the fail back to the original source withoutrebooting.

NOTE: For any operating system you use, refer to the OS-specific documentation on the SPOCKwebsite to ensure that you use compatible versions of multipath drivers and HBAs. Each boot diskmust be in its own DR group.

50 Planning the solution



6 Implementing remote replicationThis chapter describes the basic steps for setting up HP P6000 Continuous Access.

Remote replication configurationsThere are a number of options for configuring your solution to support remote replication. Fordetailed information on remote replication configurations, see “Planning the remote replicationfabric” (page 23).

Verifying array setupYour array purchase may include installation services provided by HP-authorized servicerepresentatives at local and remote sites. You should, however, verify that the arrays are set upand cabled properly for remote replication.

Installation checklistVerify that the following items are installed or configured:

• External connections from the array controllers to two (or for some controllers, four) fabricsthat are also connected to application servers (hosts)

• Internal connections from array controllers to disk enclosures and loop switches

• (Optional) HP P6000 Command View password on the array

• HP P6000 Command View on a management server connected to the fabrics that connectthe local array to the remote array

• (Optional) HP P6000 Command View on a management server connected to the fabrics thatconnect the local array to the remote array

• Storage system data replication protocol set properly

NOTE:• Make sure Fibre Channel switches are configured properly as described in “Verifying Fibre

Channel switch configuration” (page 51).• HP P6000 Continuous Access is not supported when the management server is attached

directly to the array.

Verifying Fibre Channel switch configurationTo ensure proper operation in an HP P6000 Continuous Access environment, the necessary FCswitches must be configured properly. Make sure the FC switches meet the following requirements.For more information on FC switch operation and the procedures and commands used to configurethe switch, see the following:


• Documentation for the model and version of the FC switch(es) you are usingYou can find FC switch documentation on the Manuals page of the HP Business Support Centerwebsite:http://www.hp.com/support/manualsIn the Storage section, click Storage Networking, and then select your switch product.

Remote replication configurations 51


B-series switch configurationThe following routing policies are available on B-series switches:

• Exchange-based routing—The routing path is based on the SID, DID, and OXID optimizingpath utilization for the best performance. Each SCSI exchange can take a different path throughthe fabric. Exchange-based routing requires using the Dynamic Load Sharing (DLS) feature.When this policy is in effect, you cannot disable DLS. Exchange-based routing also supportsthe following AP policies:

◦ AP shared link policy (default)

◦ AP dedicated link policyThis policy dedicates links to egress traffic and links to ingress traffic.

• Port-based routing—The routing path is based only on the incoming port and the destinationdomain.

B-series switch settings for the HP-FC protocol

NOTE: The following configuration must be used in an HP P6000 Continuous Access environmentfor all Fibre Channel switches in the path from the source array to the destination array. Thisincludes FCIP routers that are connected to the fabric.

Execute the following commands to establish the required switch settings:1. switchdisable

2. aptpolicy 1 (enable port-based routing)3. dlsreset (disable DLS)4. iodset (enable in-order delivery)5. switchenable

B-series switch settings for the HP SCSI-FCP protocol

NOTE: The HP SCSI-FCP protocol supports aptpolicy of 1 or 3, and iod enabled or disabled.The best performance in a configuration with multiple paths between source and destination isachieved using an aptpolicy of 3 and iod disabled (iodreset). Please review the Brocadeswitch documentation for a detailed discussion of these settings.

Example: The following commands set the switch settings for best performance.1. disable switch

2. aptpolicy 3 (enable exchange-based routing)DLS is enabled when aptpolicy is set to 3.

3. aptpolicy –ap 0 (enable shared link policy)4. iodreset (disable in-order delivery)5. switchenable

C-series switch configurationThe following routing policies are available on C-series switches:

• Exchange based routing—The first frame in the exchange chooses a link, and subsequentframes in the exchange use the same link. However, subsequent exchanges can use a differentlink. This provides more granularity to load balancing while preserving the order of framesfor each exchange.

• Flow based routing—All frames between the source array and the destination array followthe same links for a given flow. The link that is selected for the first exchange of the flow isused for all subsequent exchanges.

52 Implementing remote replication

C-series switch settings for the HP-FC protocol

NOTE: The following configuration must be used in an HP P6000 Continuous Access environmentfor all Fibre Channel switches in the path from the source array to the destination array. Thisincludes FCIP routers that are connected to the fabric.

Execute the following commands to establish the required switch settings:1. config terminal

2. (config)# in-order-guarantee (enable in-order delivery)3. (config)# vsan database

4. (config-vsan-db)# vsan x loadbalancing src-dst-id (load balancing policyset to Src-ID/D-ID)

5. (config-vsan-db)# end

6. copy running-config startup-config

7. config terminal

8. (config)# interface fcip (fcip #)

9. (config-if)# no write-accelerator (set write accelerator to off)10. (config-if)# end


12. show fcip summary (review your settings)• When using FCIP, the TCP send buffers must be set to 4,096 K on all FCIP profiles on both

the source and destination sites. One exception is a solution using a link less than OC3 (155Mb/s), in which case buffers must be set to 8,192 K (tcp send-buffer-size 8192).

• In-order delivery guarantees that frames are delivered to the destination in the same order inwhich they were sent by the source.

C-series switch settings for the HP SCSI-FCP protocol

NOTE: The HP SCSI-FCP protocol supports load balancing options src-dst-id orsrc-dst-ox-id, and iod enabled or disabled. The best performance in a configuration withmultiple paths between source and destination is achieved using the load balancing optionsrc-dst-ox-id and iod disabled (no in-order-guarantee). Please review the Cisco switchdocumentation for a detailed discussion of these settings.

ExampleExample: The following commands set the switch settings for best performance.1. config terminal

2. (config)# no in-order-guarantee (disable in-order delivery)3. (config)# vsan database

4. (config-vsan-db)# vsan x loadbalancing src-dst-ox-id (load balancingpolicy set to Src-OX/ID)

5. (config-vsan-db)# end


7. config terminal

8. (config)# interface fcip (fcip #)

9. (config-if)# no write-accelerator (set write accelerator to off)10. (config-if)# end


Verifying array setup 53

12. show fcip summary (review your settings)• When using FCIP, the TCP send buffers must be set to 4,096 K on all FCIP profiles on both

the source and destination sites. One exception is a solution using a link less than OC3 (155Mb/s), in which case buffers must be set to 8,192 K (tcp send-buffer-size 8192).

H-series switch configurationH-series switches only support either the HP IP Distance Gateway or the MPX200 MultifunctionRouter. The FC-to-IP gateways should be same model and software version on each side of the IPnetwork in the fabric.

NOTE: H-series FC switches are only supported with XCS 09534000 or later and the HP SCSI-FCPprotocol. For the latest information about supported firmware, see the P6000/EVA Array Streamsand the H-series FC Switch Connectivity Stream on the HP Single Point of Connectivity Knowledge(SPOCK) website at http://www.hp.com/storage/spock.You must sign up for an HP Passport to enable access.

M-series switch configurationBoth HP-FC protocol and HP SCSI-FCP protocol can be used with M-series switches. If the M-seriesswitch is installed in an environment with other model switches (for example, B-series), follow theconfiguration settings for the other (non-M-series) switch.

M-series switch settings for the HP-FC and HP SCSI-FCP protocols

NOTE: The following configuration must be used in an HP P6000 Continuous Access environmentfor all Fibre Channel switches in the path from the source array to the destination array.

The Reroute Delay (in-order delivery) must be enabled on all M-series switches (rerouteDelay1)

Verifying cablingVerify that the cabling between the arrays and Fibre Channel switches meets remote replicationrequirements. The supported cabling scheme depends on the array controller hardware and softwarefeatures, as shown in Figure 17 (page 55) through Figure 19 (page 55). In mixed arrayconfigurations, use the cabling scheme specific to each controller. For a description of all cablingoptions, as well as best practices for cabling, see the HP SAN Design Reference Guide.

NOTE:• For low-bandwidth intersite links, HP recommends using separate array ports for host I/O and

replication I/O.• When connecting the array, the even-numbered controller ports should be connected to one

fabric, and the odd-numbered controller ports should be connected to a different fabric.• On arrays running VCS 3.xxx, straight or cross-cabled connections are supported with HP

P6000 Continuous Access.

Figure 17 (page 55) shows the standard cabling scheme for remote replication on arrays withtwo-port controllers. The even-numbered ports on each controller are connected to one fabric andthe odd-numbered ports on each controller are connected to the other fabric. Figure 18 (page 55)shows the same connections for the EVA4400 single-enclosure controllers.



Figure 17 Cabling for arrays with two-port controllers

Figure 18 Cabling for EVA4400 with two-port controllers

Figure 19 (page 55) shows the standard cabling scheme for remote replication on arrays withfour-port controllers. Each controller has redundant connections to both fabrics. Even-numberedports are connected to one fabric and odd-numbered ports are connected to the other fabric.

Figure 19 Cabling for arrays with four-port controllers


Changing host port data replication settings

NOTE:• Manually setting host port preferences should be done carefully and only when absolutely

necessary. Using this feature requires advanced knowledge of array operation to ensure theexpected results are achieved.

• Host port replication settings can be managed using HP P6000 Command View, HP P6000Replication Solutions Manager, or the HP Storage System Scripting Utility. The followinginformation assumes the use of HP P6000 Command View, which provides more capabilitywhen performing this task.

• The host port preferences for EVA3000 and EVA5000 arrays should be left at the predefineddefaults.

HP P6000 Command View 9.0 or later enables the monitoring and setting of controller host portspreferences for data replication traffic. This functionality is supported on XCS 6.xxx or later andXCS 09xxxxxx or later. Host port replication settings are managed from the Data Replication FolderProperties page within HP P6000 Command View. See Figure 20 (page 57).Host port preferences are set to defaults during controller initialization. The port settings can bechanged, regardless of whether there are active DR groups on the array or not. This enables asource array to establish a unique host port priority sequence for each destination array visible tothe source: 1st – 4th for 8-port controller pairs, and 1st or 2nd for 4–port controller pairs. Thereis also a No DR host port option which blocks the creation of tunnels on the specified port, disablingall remote replication traffic for that port.The port preferences are automatically checked by the controller software at the Check intervalsetting, one minute after a change is sent to the controller software by the management software,and when a controller state change results in a data replication tunnel opening (for example, acontroller resync or link state change). The Check interval setting can be changed or disabled. Ifport checking is disabled and changes to the port preferences are saved, the changes will not beinvoked until port checking is re-enabled or a controller state change occurs.

IMPORTANT: Even when port checking is not enabled, the port preferences that were saved willbecome active with controller state changes.

A port actively forwarding data replication traffic may be changed to No DR. This change movesthe tunnel to the next highest priority port when the next port preference check occurs. Changinga host port preference to NO DR does not cause the remaining host port values to be reset. Forexample, if the host port with 1st priority is set to No DR, the preferences for the 2nd, 3rd, and4th host ports will remain in effect and will not change value. In this example, the controller softwarewould make the host port with a value of 2nd the highest priority host port available on thecontroller.Purging a node removes it from the Remote Nodes list. A node can only be purged when thereare no DR groups between the selected source array and the array to be purged and the array isunreachable. It may be necessary to purge a node when it is removed from an environment, orwhen remote replication is no longer in use. Purging a node deletes it from the Remote System liston the Host port data replication settings property page and the Remote System Connection statusproperties page on the View remote connections tab.The Reset to defaults button returns all host port priority and the port checking values to theirdefaults.


Figure 20 Host port data replication settings

Verifying path statusThe current remote connection path status can be checked from HP P6000 Command View. In thenavigation pane, select the Data Replication folder for the storage system. The Data ReplicationFolder Properties page opens. Click View remote connections to view the Remote System ConnectionsStatus page. To view additional information, click the path details icon. A window opens showinglocal and remote controller host ports, paths and path status.A host port can have one of the following path status values:

• Available. The host port has an available path to the target storage system; and, the host portcan create a tunnel to the target storage system.

• Disabled. One of the following conditions exists:

The host port has been intentionally disabled. The port preference has been set to NoDR. No DR tunnels can be created on the host port.

◦

◦ There is a remote replication protocol mismatch. One storage system is set to HP FC DataReplication Protocol and the other storage system is set to HP SCSI FC Compliant DataReplication Protocol. For more information, see “Planning the data replication protocol”(page 38).

• DR active. The host port has a remote replication tunnel.

• No Path. No path exists between the host ports on the storage system pair, either due to thehost ports not being connected to the fabric, improper zoning, or a hardware failure.

• Unavailable. The host port has reached the limit for tunnels on the port. The existing tunnelsare operating normally but no additional tunnels can be created. This can be resolved byensuring that additional host ports are available for tunnel creation. Consider changing hostport preferences by setting multiple host ports to the same priority, or by zoning changes.

NOTE: There is no host port tunnel limit for storage system pairs running XCS 0953x000or later with the remote data replication protocol set to HP SCSI FC Compliant Data ReplicationProtocol.


Installing replication licensesWhen you purchase HP P6000 Continuous Access, you receive a replication license for eacharray (local and remote) in a remote replication relationship. Replication licenses are based onthe amount (in TB) of replicated data on each array. License kits include instructions for retrievingelectronic license keys and for installing the keys in HP P6000 Command View. Entering the keyson the HP P6000 Command View license page activates remote replication features on specifiedarrays. For license offerings, see the product QuickSpecs on the HP P6000 Continuous Accesswebsite at http://h18006.www1.hp.com/products/storage/software/conaccesseva/index.html.Follow the instructions provided in the license kit for retrieving electronic license keys from the HPLicense Key Renewal website and for installing the keys using HP P6000 Command View. Licensekeys arrive in email within 48 hours after you submit the credentials from the license kit. Install thelicense keys on each active and standby management server at the local and remote sites.

Installing HP P6000 Replication Solutions Manager (optional)For additional replication capabilities, install HP P6000 Replication Solutions Manager on localand remote management servers. For more information on the unique features of this software, aswell as installation requirements and instructions, see the HP P6000 Replication Solutions ManagerInstallation Guide.

DC-Management and HP P6000 Continuous AccessWhen using DC-Management (dynamic capacity management) in HP P6000 Continuous Accessenvironments, you must ensure that DC-Management is installed on each management server andthat a DC-Management license is installed on both the local and remote management server runningHP P6000 Replication Solutions Manager. For more information on DC-Management, see the HPP6000 Replication Solutions Manager User Guide or the HP P6000 Replication Solutions Manageronline help.

Creating fabrics and zonesThis section identifies the recommended fabric configurations and zoning for HP P6000 ContinuousAccess environments. Switch zoning allows incompatible resources to coexist in a heterogeneousSAN. Use switch management software to create separate zones for incompatible hosts in theSAN. In each zone, include the arrays that the host will access before and after a failover. Arraycontroller ports can be in overlapping zones.For instructions for creating zones, see your switch user guide and follow the best practices in PartII of the HP SAN Design Reference Guide.

Fabric configuration drawingsThe drawings in this section illustrate the preferred method for implementing remote replicationusing different fabric configurations. These configurations optimize replication and facilitatesupportability. The drawings represent physical configurations created using discreet hardwarecomponents. However, you can create the same configurations by using zoning to create logicalfabrics.


http://h18006.www1.hp.com/products/storage/software/conaccesseva/index.html

Two-fabric configurationFigure 21 (page 59) through Figure 23 (page 61) show two-fabric connection configurations. Inthese configurations each fabric is used for both host I/O and replication.

• Figure 21 (page 59) shows the basic two-fabric connections.

• Figure 22 (page 60) shows the two-fabric connection used between an EVA3000/5000(four–port controller pair) and an EVA8x00 (eight–port controller pair). These connections arealso used for the EVA4400 controller without the embedded FC switch.

• Figure 23 (page 61) shows the two-fabric connection used with the embedded switch EVA4400controllers. The Fibre Channel switch functionality is integrated into the EVA4400 controllers.

Figure 21 Two-fabric configuration

6. Fibre Channel switches1. Data center 1


8. Intersite link3. Array controller pair

9. Host I/O and replication fabric4. Management server

10. Intersite link5. Hosts

Creating fabrics and zones 59

Figure 22 Two-fabric configuration (EVA3000/5000 to EVA8x00)




9. Host I/O and replication fabric4. Management server



Figure 23 Two-fabric configuration (EVA4400 with embedded Fibre Channel switch)

6. Replication fabric1. Data center 1

7. Intersite link2. Data center 2

8. Replication fabric3. Array controller pair with embedded Fibre Channelswitches

9. Intersite link4. Management server

5. Hosts

NOTE:• On an EVA4400 with the embedded switch option, the connections between controller host

ports FP1 and FP2 and controller switch ports 0 and 11 are internal to the controller andcannot be changed.

• The World Wide ID (WWID) (for example XXX8) associated with each controller host port isshown.

HP P6000 Command View management connections in five-fabric and six-fabric configurationsThe connections for HP P6000 Command View management servers have been modified to separateHP P6000 Command View management traffic from HP P6000 Continuous Access replicationtraffic on the EVA controller host port (see Figure 27 (page 66), Figure 28 (page 68), andFigure 29 (page 69)). In the original connection configuration, the HP P6000 Command Viewserver HBA ports are connected directly to the Fibre Channel switches in the replication fabrics.HP still supports this connection but the HP P6000 Command View response times may be slower.This occurs because the HP P6000 Command View server traffic must compete with HP P6000Continuous Access traffic using the same host port on the array. The original configurationconnections are shown in Figure 24 (page 62), Figure 25 (page 63), and Figure 26 (page 64).These configurations ensure the fabrics will not merge and fabric changes are isolated.


Figure 24 Five-fabric configuration


7. Host I/O fabric2. Data center 2

8. Host I/O fabric3. Array controller pair

9. Replication fabric4. Management server



Figure 25 Six-fabric configuration (eight–port controller pairs)




10. Host I/O fabric4. Management server

11. Replication fabric5. Hosts

12. Intersite link6. Fibre Channel switches


Figure 26 Six-fabric configuration (four–port controller pair to eight–port controller pair)




10. Host I/O fabric4. Management server

11. Replication fabric5. Hosts

12. Intersite link6. Fibre Channel switches

The new configuration connections are shown in Figure 27 (page 66), Figure 28 (page 68), andFigure 29 (page 69). For additional details describing these zoned solutions, see “Zoning bestpractices for traffic and fault isolation” (page 70).

NOTE: These configurations can cause the fabrics to merge in to a single fabric unless thenecessary steps are taken.When creating an intersite FCIP link using B-series or C-series routers, the respective LSAN andIVR functionality can provide SAN traffic routing over the FCIP connection while preventing themerging of the two sites' fabrics in to a single fabric. LSANs and IVR enable logical fabric separationof the two sites, ensuring that a change on one site's fabric does not affect the other site.The HP FCIP Distance Gateways (MPX110) will allow the fabrics on both sites to merge into asingle large fabric. SAN traffic isolation can still be accomplished with the FCIP Distance Gatewaysusing SAN zoning, but this will not provide fabric separation. When using the FCIP DistanceGateways, fabric configuration changes should be made carefully, and it may be desirable todisable the ISL until all changes are complete and the fabric is stable.

The HP P6000 Command View management server in each of the five-fabric and six-fabricconfigurations now connects directly to the Fibre Channel switches used for host I/O. The host I/Ofabric switch is also connected to the appropriate replication fabric switches, providing acommunication path from the management server to the remote array. The management server


HBA ports are now zoned to use the same ports on the array controller as other server traffic, andare also zoned to see the remote array across the replication fabric.Using switch zoning, you can separate host I/O traffic from HP P6000 Continuous Access trafficin each data center. If FCIP communication devices are used to create the intersite link and mergingof fabrics is not desired, the Fibre Channel Routing capability is necessary to ensure that the fabricson the each side of the replication intersite link do not merge. See the HP SAN Design ReferenceGuide for the latest supported Fibre Channel routers.


A single physical fabricFigure 27 (page 66) shows a single physical fabric zoned into five logical fabrics. Four zones arededicated to host I/O, and a single zone is used for replication.

NOTE: To compensate for the SPOF in a five-zone solution (the intersite link [10]), HP recommendsthat availability be a QoS metric on the intersite link.

Figure 27 Single physical fabric with five zones


7. Host I/O zone12. Data center 2

8. Host I/O zone13. Array controller pair

9. Replication zone4. Management server

10. Intersite link5. Hosts1 The zones depicted in the figure above as yellow or green should not be zoned across the sites. Each site should have

a unique yellow and green zone.


Dual physical fabric with six zonesFigure 28 (page 68) shows a dual physical fabric with six zones used between eight–port controllerpairs. Four zones are dedicated to host I/O and two zones are dedicated to replication.Figure 29 (page 69) shows the connections used when one four-port controller pair is used.

NOTE:• In a dual physical fabric with a six-zone configuration, each HP P6000 Continuous Access

relationship must include at least one EVA8x00 or one EVA6400.• When using a dual physical with a six-zone configuration with fabric zoning, ISLs cannot be

included in the zones. See Figure 28 (page 68). Replication can be load balanced acrossISLs due to the preferred port algorithm and by preferring DR groups to both controllers onthe array. Controller software releases prior to XCS 6.xxx do not implement the preferred portalgorithm for tunnel creation and cannot guarantee proper I/O load balancing regardless ofwhich controller DR groups are preferred to. Not properly load balancing DR groups acrosscontrollers may result in one of the ISLs being overloaded, negatively impacting replicationperformance.


Figure 28 Dual physical fabric with six zones (eight-port controller pairs)


8. Replication zone2. Data center 2


10. Host I/O zone14. Management server


11. Replication zone5. Hosts

12. Intersite link6. Fibre Channel switches1 The zones depicted in the figure above as yellow or green should not be zoned across the sites. Each site should have


Figure 29 Dual physical fabric with six zones (four-port controller pair to eight-port controller pair)


8. Replication zone2. Data center 2


10. Host I/O zone14. Management server

11. Replication zone5. Hosts

12. Intersite link6. Fibre Channel switches1 The zones depicted in the figure above as yellow or green should not be zoned across the sites. Each site should have


Best practices for using zones with HP P6000 Continuous AccessObserve the following when using zones with HP P6000 Continuous Access.

• The even-numbered controller host ports should be included in one zone, and the odd-numberedhost ports should be included in a different zone.

• In configurations with eight-port controller pairs, use host ports F1 and F2 for host I/O, anduse ports F3 and F4 for replication when setting up either a five or six zone configuration.For five zone configurations it is acceptable to use a single port per controller for replicationif you don't want to dedicate two ports per controller.


• When adding array controllers to a zone, use the controller port World Wide Port Name(WWPN), not the node WWN. For example, use the WWPN 5000-1FE1-001A-012A, notthe WWN 5000-1FE1-001A-0120.

• When creating a replication zone, include only arrays that have an HP P6000 ContinuousAccess relationship with each other. Avoid including other arrays in the zone.

• Zoning allows you to enforce supported maximum visible connections. Create separate zonesfor resources that exceed the following:

◦ Maximum number of arrays in the SAN

◦ Maximum number of HBAs per array controller (see Part III of the HP SAN DesignReference Guide)

◦ Maximum number of switches in the SAN (see Part II of the HP SAN Design ReferenceGuide)

• When setting up specific HP P6000 Continuous Access replication zones, HP recommendsthat you exclude all servers from these zones.

Zoning management serversManagement servers must be in the same zones as the local and remote array host ports that areused for the intersite links. Only one server at a time can be used to manage an array. However,you should include one active management server and one standby management server in eacharray management/intersite link zone.

Zoning best practices for traffic and fault isolationThis section describes how to use switch zoning to achieve two important benefits when using HPP6000 Continuous Access: traffic isolation and fault isolation. Traffic isolation separates host I/Otraffic from HP P6000 Continuous Access replication traffic. This prevents excessive latency, causedby insufficient ISL bandwidth or line quality issues, from negatively impacting host I/O performance.Fault isolation is achieved through the use of multiple zones, which facilitates the quick isolationof SAN components when a disruption occurs. This zoning technique also supports the recommendedpractice of isolating an initiator with its targets; for example, zoning a host’s HBA ports with thehost ports of a target array. The initiator-to-target port zoning is applicable to all initiator-targetrelationships, including the HP P6000 Command View server-to-array and source array-to-destinationarray communications.

NOTE: This information is applicable to all HP P6000 Continuous Access implementations butis particularly important in configurations using FCIP intersite links. See “FCIP gateway zoningconfigurations” (page 95) for more information on FCIP configurations.

Three types of zones are used for traffic and fault isolation.

• Host I/O zones—The I/O hosts are each zoned separately to the host ports of the targetedarray. If the configuration includes multiple arrays, additional zones are created to isolate theI/O hosts HBA ports with the additional arrays. Host fan-out configurations are shown in thefollowing sections.

• Replication zone—The replication zone includes only the array host ports intended to provideHP P6000 Continuous Access replication traffic. The ports selected from each array shouldbe similar. For example, use ports 1 and 3 from a pair of 8-port controllers or use FP1 froma 4-port to an 8-port relationship. This zone limits the FP ports that an array can access forcreation of HP P6000 Continuous Access communication paths. When additional array pairs


are placed into the configuration, separate replication zones should be created for those pairsof arrays.If array system fan-out is required, then the additional array should be added to a newreplication zone. Only arrays that will participate in data replication relationships should bezoned together. Additional arrays (up to supported limits) can be added to either site. Seethe HP P6000 Enterprise Virtual Array Compatibility Reference for the number of arrayssupported for system fan-out.

• HP P6000 Command View management zones—The zones for a HP P6000 Command Viewmanagement server must include both the source and destination arrays to enable the creationof DR groups and proper management of the arrays. The management server must also haveat least one host port from each controller of the arrays zoned with the HP P6000 CommandView management server HBA. Additional array pairs are zoned in a similar manner for eachsite. If an additional array is added to either site and it will participate in a DR relationship,then two additional zones should be created for each of the HP P6000 Command Viewmanagement server HBA ports and the additional array’s host ports.

NOTE: The configurations shown assume HP P6000 Command View is installed on a standalone server. HP P6000 Command View could also be installed on an application serverrunning a supported version of Windows. When a server is used as both an application serverand HP P6000 Command View management server, virtual disks must be properly presentedfrom arrays to the intended hosts. Unintended cross-site virtual disk presentations should beavoided.A multipathing solution must be implemented that isolates the host I/O traffic to the targetedI/O array host ports paths, which will maintain the desired traffic isolation. See the appropriatemultipathing documentation for path selection setup. Using a server for both host I/O and HPP6000 Command View traffic should be avoided if traffic isolation is not available.

These zoning techniques provide a lower cost option than using discrete components to create themultiple fabrics shown in “Fabric configuration drawings” (page 58). Zoning does not providephysical separation of replication traffic over the intersite communication paths. These paths mayuse dark fiber or FCIP connections between the local and remote sites. The lack of physicalseparation in the configurations included here requires the zoning configuration be such that theintersite communications be used to service only HP P6000 Continuous Access replication and HPP6000 Command View management traffic. Application I/O should be limited to local arrays.Cross-site presentation of virtual disks will result in host I/O traffic across the ISLs which may impactHP P6000 Continuous Access performance. Cross-site presentations of virtual disks should beavoided without a careful historical analysis of the utilization rate on the intersite communicationpath.

Understanding the zoning drawingsThe following sections illustrate the zones used for single-fabric and dual-fabric configurations. Atopology drawing showing the physical components for each configuration is shown first. Thezoning drawings use red and blue shading to identify the ports that comprise each zone. The portsincluded in a zone are further identified using the same colors. Any port that is not colored is notincluded in a zone.

Recommended single-fabric zoning configurationsThe following zoning can be accomplished using a single fabric. This is a reduced availabilityconfiguration consisting of a single switch at both the local and remote sites.


IMPORTANT: This reduced availability configuration is not recommended for productionenvironments requiring high availability. The single switch on each site represents an SPOF for thehost I/O and the HP P6000 Continuous Access replication traffic.

• Single-fabric components—Figure 30 (page 73) shows the various components that comprisethe single-fabric topology.

• Host I/O zones—Figure 31 (page 74) and Figure 32 (page 75) show the ports used to createthe host I/O zones.

• HP P6000 Command View management zones—Figure 33 (page 76) and Figure 34 (page77) show the ports used to create the HP P6000 Command View management zones.

• Replication zone—Figure 35 (page 78) shows the ports used to create the HP P6000 ContinuousAccess replication zone. Figure 36 (page 79) and Figure 37 (page 80) show replicationzones when array system fan-out is used.


Figure 30 Single-fabric zoning components

6. Site 2 Fibre Channel switch1. Site 1 Array controller pair

7. Site 2 management serve2. Site 1 Fibre Channel switch

8. Site 2 host3. Site 1 host

9. Intersite link4. Site 1 management server

5. Site 2 Array controller pair


Figure 31 Single-fabric host I/O zones: sheet 1

Zone 2 portsZone 1 ports

Site 2 host port HBA1Site 1 host port HBA1

Site 2 Array controller A port FP1Site 1 Array controller A port FP1

Site 2 Array controller B port FP1Site 1 Array controller B port FP1


Figure 32 Single-fabric host I/O zones: sheet 2






Figure 33 Single-fabric HP P6000 Command View local management zones


Site 2 management server port HBA1Site 1 management server port HBA1





Figure 34 Single-fabric HP P6000 Command View remote management zones







Figure 35 Single-fabric replication zone

Zone 9 ports

Site 1 Array controller A port FP2

Site 1 Array controller B port FP2

Site 2 Array controller A port FP2

Site 2 Array controller B port FP2


Figure 36 Single-fabric replication zone fan-out: sheet 1

Zone 10 ports

Site 1 Array (1) controller A port FP2

Site 1 Array (1) controller B port FP2




Figure 37 Single-fabric replication zone fan-out: sheet 2

Zone 11 ports





Recommended dual-fabric zoning configurationsThis is a high availability configuration consisting of two switches per site, which creates two distinctextended fabrics that span the two sites. This configuration eliminates the SPOF for host I/O traffic.

• Dual-fabric components—Figure 38 (page 81) shows the various components that comprisethe dual-fabric topology.

• Host I/O zones—Figure 39 (page 82) and Figure 40 (page 83) show the ports used to createthe host I/O zones.

• HP P6000 Command View management zones—Figure 41 (page 84) through Figure 44 (page87) show the ports used to create the HP P6000 Command View management zones.

• Replication zones—Figure 45 (page 88) shows the ports used to create the HP P6000Continuous Access replication zones. Figure 46 (page 89) and Figure 47 (page 90) showreplication zones when array system fan-out is used. Figure 48 (page 91) and Figure 49 (page92) show replication zones used to create port isolation when array system fan-in or fan-outis used in a configuration that includes an EVA3000/5000. Figure 50 (page 93) andFigure 51 (page 94) show the replication zones when using a 4-port controller pair and an8-port controller pair.

NOTE: See “FCIP gateway zoning configurations” (page 95) if you are creating a dual-fabricconfiguration using FCIP gateways.


Figure 38 Dual-fabric zoning components

7. Site 2 host1. Site 1 Array controller pair

8. Site 2 management server2. Site 1 host

9. Site 2 Fibre Channel switch3. Site 1 management server

10. Site 2 Fibre Channel switch4. Site 1 Fibre Channel switch

11. Intersite link5. Site 1 Fibre Channel switch

12. Intersite link6. Site 2 Array controller pair


Figure 39 Dual-fabric host I/O zones: sheet 1






Figure 40 Dual-fabric host I/O zones: sheet 2






Figure 41 Dual-fabric HP P6000 Command View local management zones: sheet 1






Figure 42 Dual-fabric HP P6000 Command View local management zones: sheet 2






Figure 43 Dual-fabric HP P6000 Command View remote management zones: sheet 1






Figure 44 Dual-fabric HP P6000 Command View remote management zones: sheet 2






Figure 45 Dual-fabric replication zone







Figure 46 Dual-fabric replication zone fan-out: sheet 1


Site 1 Array controller A port FP4Site 1 Array (1) controller A port FP3

Site 1 Array (1) controller B port FP4Site 1 Array (1) controller B port FP3

Site 1 Array (13) controller A port FP4Site 1 Array (13) controller A port FP3



Figure 47 Dual-fabric replication zone fan-out: sheet 2







NOTE: “Dual-fabric replication zone fan-in/fan-out for port isolation: sheet 1” (page 91) and“Dual-fabric replication zone fan-in/fan-out for port isolation: sheet 2” (page 92) show a mixedarray environment that includes an EVA3000/5000 (item 1). In this type of configuration, changesshould be made to isolate host ports to eliminate the possibility of reduced replication performancecaused by the reduction in resource utilization. Prior to creation of DR groups, the host ports shouldbe isolated using the zoning shown. This zoning configuration isolates host ports on arrays 1 and6 from creating connections on the same ports of array 13.

Figure 48 Dual-fabric replication zone fan-in/fan-out for port isolation: sheet 1

Zone 19 ports

Site 1 EVA3000/5000 (1) controller A port FP1

Site 1 EVA3000/5000 (1) controller B port FP1




Figure 49 Dual-fabric replication zone fan-in/fan-out for port isolation: sheet 2

Zone 20 ports






Figure 50 Dual-fabric replication zone 4-port to 8-port controllers (straight-cabled)


Site 1 Array controller B port FP2Site 1 Array controller A port FP1




Figure 51 Dual-fabric replication zone 4-port to 8-port controllers (cross-cabled)


Site 1 Array controller B port FP2Site 1 Array controller A port FP2



NOTE: This zoning is used when the 4-port controller pair is configured with FP1 cross-cabledas shown. The cross cabling configuration shown is applicable to EVA3000/5000 array modelsrunning VCS version 3.xxx. If the cabling configuration for these models is cross-cabled, the zoningshown is applicable. EVA3000/5000 arrays that use straight cabling should follow the zoningrecommendation shown in Figure 50 (page 93). More recent 4- port controllers (EVA4400) donot require cross-cabling. Use the zoning applicable for your cabling configuration. It is notnecessary to change an existing straight-cable configuration to a cross-cabled configuration forHP P6000 Continuous Access.


FCIP gateway zoning configurationsWhen using FCIP gateways as the interconnect between sites, consider the following:

• HP B-series and HP C-series switch products can be used to create the configuration shownin Figure 38 (page 81). The zoning options shown in “Recommended dual-fabric zoningconfigurations” (page 80) can be used with B-series and C-series switch products. Theseproducts allow independent fabrics on each site to access objects on the other site. To enablethis functionality, B-series switches use LSANs and C-series switches use VSANs. For moreinformation, see the HP SAN Design Reference Guide.

NOTE:

◦ B-series or C-series FCIP-capable switches must have the LSAN or capability explicitlyconfigured to prevent fabrics from merging.

◦ The array may be connected to the router's FC ports directly or to a fabric switch that isconnected to the router. The B-series and C-series switches that are LSAN or VSAN capablemay be connected to the HP FCIP Distance Gateway. The fiber channel routing functionalityin the B-series and C-series switches is supported across the FCIP link provided by the HPFCIP Distance Gateway.

◦ The array may not be connected directly to the FC ports of an HP FCIP Distance Gatewayproduct.

Additional information is available in the HP SAN Design Reference Guide or in the ContinuousAccess section of the Applications Notes on the HP SPOCK website. Review the applicabledocuments listed under the Remote Replication section of the SPOCK website, which is locatedat http://www.hp.com/storage/spock.

• Figure 52 (page 96) shows a data replication environment using mpx110 FCIP gateways asthe interconnect between sites. This configuration differs from the standard dual-fabricconfiguration in that the mpx110 creates two merged fabrics. For more information on thezones used for this configuration, see “Recommended dual-fabric zoning configurations”(page 80).Disruptions in the WAN can cause a merged fabric to split into individual fabrics and thenre-merge into a single fabric when the connection is reestablished. See the HP SAN DesignReference Guide for more information on HP FCIP Distance Gateway functionality.

• Use of HP IP Distance Gateway (mpx110) or MPX200 Multifunction Router as shown inFigure 52 (page 96) is the recommended supported configuration for H-series switches.



Figure 52 FCIP gateway zoning configurations using the mpx110

8. Site 2 management server1. Site 1 Array controller pair

9. Site 2 Fibre Channel switch2. Site 1 host

10. Site 2 Fibre Channel switch3. Site 1 management server



13. mpx110 gateways6. Site 2 Array controller pair

7. Site 2 host

Configuring hostsConfigure native or installed multipathing software on all hosts in remote replication configurations.Multipathing software redirects I/O requests from a failed path to the alternate path, preventingdisruptions in data access if the path to the array fails. See your multipathing documentation forinstallation and configuration information.

Configuring disk groups for remote replicationDisk groups are created to meet performance and single array availability needs. However, youmust consider HP P6000 Continuous Access requirements when choosing a disk group for thewrite history log. There must be enough space in the disk group for the log. Of additional concernmay be the destination array disk group, which must contain enough disk drives to satisfy the writeI/O load imposed by HP P6000 Continuous Access. HP P6000 Continuous Access should betaken it into account when evaluating the overall performance of the array. For more information,see “Planning disk groups” (page 35).

Creating and presenting source virtual disksVirtual disks, created using HP P6000 Command View, are the primary storage objects on thearray. When creating source virtual disks for a DR group, select the preferred controller carefully.Balancing DR groups across controllers contributes to the efficient utilization of remote replicationresources and balances the I/O load. You should ensure that the DR groups imposing the heaviestworkloads are distributed across the controllers.For information on creating virtual disks, see the HP P6000 Command View Online Help.


Selecting a preferred controllerThe following are important points to remember when selecting a preferred controller for DR groupmembers:

• The same preferred controller is used for all members of a DR group. The preferred controllervalue used for each virtual disk is set automatically based on the value assigned to the firstDR group member. Ensure that the first member you add to the DR group is set to the desiredpreferred controller.

• On XCS 6.200 or later and 09003000 or later, the preferred controller value used for theDR group source virtual disks is automatically used for all destination virtual disks. On earlierversions of controller software, you should manually set the DR group destination virtual disksto the same preferred controller value used for the source.

• If the preferred controller value for the DR group source is set to No preference, differentpreferred controllers may be used for the DR group source and destination.

• If the DR group source and destination use different preferred controllers, the DR relationshipwill function properly but the load may not be balanced for optimal performance.

• Changing the preferred controller for an existing DR group member automatically changesall DR group members to the new value. On XCS 6.200 or later and 09003000 or later,changes made to the DR group source members are automatically propagated to the DR groupdestination members. However, changes made to the DR group destination members are notpropagated to the source members.

NOTE:• HP P6000 Command View refers to the preferred controller as Preferred path/mode and the

controller that currently owns the virtual disk as Managing Controller. The HP Storage SystemScripting Utility refers to the controller that currently owns the virtual disk as online controller.

• Setting the Preferred path/mode for a virtual disk enables transition of controller ownership.To transition a virtual disk to the other controller, select the appropriate Preferred path/modefor the controller Path A (or B)-Failover/failback and save the change. The presented virtualdisk will transition to the new controller after the change is saved. For the EVA4400 controller,HP P6000 Command View displays Controller 1 or Controller 2 as the Managing Controllerfor the selection of Path A or Path B respectively.

• Because of the effort required to transition a DR group and associated members betweencontrollers, HP recommends that the Preferred path/mode of a DR group member LUN onlybe changed during light host loads. The Preferred path/mode can also be changed during acopy or when a merge is in progress.

Using the failover/failback settingThe recommended setting for virtual disks that are members of a DR group is failover/failback.This setting ensures that following a controller state change that results in a LUN transition, theoriginal managing controller regains ownership of the LUN. This behavior maintains the DR groupload balancing configured by the user. If the failover/failback setting is not used for DR groupmember virtual disks, the user must manually transition the virtual disks back to the original managingcontroller to re-establish DR group load balancing. HP Storage System Scripting Utility scripts canalso be created for rebalancing the DR groups.The user must determine if the multipathing solution on the host the virtual disk is presented to hasthe ability to react to Unit Attentions generated by a LUN transition. There are some instances ofLUN transition that do not generate a Unit Attention. The multipathing solution should provide amechanism to handle this occurrence. Consult the appropriate operating system multipathingdocumentation to determine if this functionality is available.

Creating and presenting source virtual disks 97

Using the failover only settingThe failover only setting should be used for virtual disks that are presented to a host using HPSecure Path. This setting automatically redirects I/O to the alternate controller if the preferredcontroller becomes unavailable, but enables the host server to use HP Secure Path settings orcommands to control the return to the preferred controller when it becomes available.For virtual disks that are presented to a host using other multipathing software, select either failoveronly or failover/failback for non-DR group member virtual disks.

Presenting virtual disksPresenting virtual disks is required to allow host access. Use HP P6000 Command View or HPP6000 Replication Solutions Manager to present source virtual disks to the host servers that willuse the storage. For the procedure for presenting virtual disks, see the application online help.Presenting virtual disks to hosts is an array requirement. You must also make virtual disks accessiblefrom the host's perspective. Use host operating system tools to discover and mount the source virtualdisks (disk devices) as required by the host.

Adding hostsAdding a host makes it easier to define a path between the host HBAs and the virtual disks in anarray. Use HP P6000 Command View to add each host that needs access to the source array. Forconvenience, you can perform this and subsequent HP P6000 Command View procedures on thelocal management server and copy the finished configuration to the standby and remotemanagement servers.To present a virtual disk to a server so the server can perform I/O to that disk, map the virtual diskto the server WWN using HP P6000 Command View. For more information on presenting virtualdisks, see the HP P6000 Command View Online Help.

Creating DR groupsBefore you create DR groups, ensure that:

• Local and remote arrays are online and accessible to the management server.

• ISLs are operating properly.

• HP P6000 Command View on the active local management server has control of the localand remote arrays.

After you create the DR groups, you can divide the management responsibilities for multiple arraysbetween the local and remote management servers. For instructions on changing the managementserver that is managing an array, see the HP P6000 Command View User Guide.Use HP P6000 Replication Solutions Manager or HP P6000 Command View to create DR groupson the source array. At a minimum, you must specify a source virtual disk and a destination array.The array software creates a corresponding DR group and virtual disk on the destination array.For more information, see “Planning DR groups” (page 36).

Specifying virtual disksSelect one virtual disk to create the DR group. Add other virtual disks as needed to ensure that alldata for one application is in one DR group. For optimum failover performance, limit the virtualdisks in a DR group to as few as possible, and do not group virtual disks that are assigned toseparate applications.To be eligible for inclusion in a DR group, a source virtual disk:

• Cannot be a member of another DR group

• Cannot be added to a destination DR group


• Cannot be a snapshot

• Cannot be a mirrorclone

• Must be in normal operational state

• Must use mirrored write cache (the default)The maximum number of virtual disks in a DR group and the maximum number of DR groups perarray vary with controller software versions. For current supported limits, see the HP P6000 EnterpriseVirtual Array Compatibility Reference.

Adding members to a DR groupWhen adding new members to an existing DR group, it is important to ensure that I/O consistencyof the destination virtual disks in the DR group is maintained at all times. This ensures dataconsistency should it become necessary to fail over to the destination array.To ensure I/O consistency of the destination array, the addition of new DR group members andthe accompanying normalization should occur before the new members are presented to anapplication server for use. If the new virtual disks are used by an application server before theyare added to the DR group, when normalization begins the destination DR group members will bein a data-inconsistent state until the new members have completed normalization. By adding thenew members to the DR group and allowing normalization to complete before presenting them tothe application server, I/O consistency is maintained at all times on the destination volumes in theDR group.Use the following steps when adding virtual disks to a DR group to ensure that the data on thedestination array remains I/O consistent at all times. These steps apply to all synchronous andenhanced or basic asynchronous DR groups using XCS versions 6.200 or later.1. Add the new virtual disks to the DR group.

The normalization process begins and should be allowed to complete before presenting thenew members to the application server for use. During normalization, the virtual disk memberson the destination array will be I/O consistent to the application. Because the applicationserver has not yet had the new members presented to it, it cannot write to the new members.Consequently, the application server does not need the new members for an I/O consistentview of application data if a failover to the destination array is required.

2. When normalization of the new members is complete, present the virtual disks to the applicationserver.Data now written to the new virtual disks will be I/O consistent within the DR group becauseof the guaranteed write ordering for multiple member DR groups.

Selecting replication modeSelect the replication mode when you create a DR group. Synchronous mode is the default, providingidentical copies on local and remote arrays as long as live replication is occurring. Asynchronousmode may provide faster response to host server requests, but it does not ensure that data hasbeen replicated to the remote array before the host is told that the I/O is complete. The choice ofwrite mode has design implications and depends on business requirements. For detailed descriptionsof synchronous and asynchronous modes, see “Choosing a write mode” (page 20).

Specifying DR group write history log location and sizeYou can specify the size and location of the DR group write history log when you create a DRgroup. The log size and location are dependent on the controller software version. For moreinformation on DR group write history log, see “Planning for DR group write history logs” (page 42).

Creating DR groups 99

Presenting destination virtual disksAfter creating the DR groups, you can present the destination virtual disks to the remote hosts inany of the following modes. You can use HP P6000 Command View, HP P6000 ReplicationSolutions Manager, or HP Storage System Scripting Utility to present destination virtual disks toremote hosts.

• None—The virtual disk cannot be presented to any hosts. (HP Storage System Scripting Utilityuses the term “disable” for this mode.)

• Read Only—The virtual disk can be presented to hosts for read only.

• Inquiry Only—The virtual disk can be presented to hosts for SCSI inquiry commands only. Noreads or writes are allowed. (HP P6000 Replication Solutions Manager uses the term “NoRead” for this mode.)

NOTE: A destination DR group member should not be presented to the same host that is accessingthe source member of the DR group if the presentation mode is Read Only or Inquiry Only.

Backing up the configurationBack up your storage and replication configuration now and whenever it changes. Regular backupsare essential for effective disaster recovery. You can use the initial backup to re-create theconfiguration on remote and standby management servers. For backup procedures, see “Backingup replication configuration” (page 126).

Setting up remote and standby management serversUse the backup from the local management server to duplicate the replication configuration onremote and standby management servers. Before importing the configuration from the local instanceof HP P6000 Replication Solutions Manager, you must assume active management of the arraysin the configuration using HP P6000 Command View on the remote or standby management server.For the procedure for acquiring control of the arrays, see the HP P6000 Command View UserGuide.After setting up all management servers, acquire control of the arrays on the local managementserver. Only one management server at a time can manage an array.

Testing failoverBefore you use the new DR groups, practice both planned and unplanned failovers. For failoverprocedures, see “Planned failover” (page 105) and “Unplanned failover” (page 108).


7 Failover and recoveryThis chapter provides information about failing over and resuming operations after a planned orunplanned loss of operation. The several scenarios describe situations you may encounter, withprocedures for handling each scenario.

Failover exampleFigure 53 (page 102) shows data replication among DR groups at three locations. Arrays 1 and 4are at the local site, and arrays 2 and 5 are at a remote site. On the local site, array 1 containssource virtual disks in a DR group (replicating to array 2), and array 4 contains destination virtualdisks (replicated from array 5). If the arrays at the local site become unavailable, the DR groupon array 2 fails over and becomes source virtual disks (in failover state), making the destinationvolumes in the DR group available to hosts connected to array 2, so that processing can resumeat the remote site using array 2. On array 5, the DR group begins logging until the failed site isre-established or replaced with another destination. Array 2 will also start to log if the replicationmode being used is synchronous.

Failover example 101

Figure 53 DR groups before and after failover

6. Local site1. Source array before failover

7. Remote site2. Destination array before failover

8. Failover3. Replication

9. Logging4. Destination array

5. Source array

102 Failover and recovery

Planning for a disasterPlanning helps to minimize downtime caused by a disaster. When planning for disaster recovery,include the following:

• Ensure that you have a supported disaster-tolerant solution.

NOTE: Not all supported cable configurations will provide for dual fabrics and ISLs.

• Have at least one management server available at every site in case of a hardware orcommunication failure.

• Verify that each destination virtual disk within a DR group has been presented to a host. Thisallows the host access to the virtual disk immediately after a failover.

• Ensure that local and remote hosts have the latest patches, virus protection, HP Storage SystemScripting Utility, and multipathing software versions for the specific operating system.

• Keep your configuration current and documented at all sites. Install the latest versions ofcontroller software, HP P6000 Command View, and HP P6000 Replication Solutions Manager.

• Keep a record of your virtual disks, DR groups, and host volume and volume group names.Capture the configuration information after each significant change or at scheduled intervals.See “Backing up replication configuration” (page 126).

• Keep HP P6000 Replication Solutions Manager on every management server up-to-date withconfiguration changes. See the HP P6000 Replication Solutions Manager online help for theprocedure for exporting and importing the HP P6000 Replication Solutions Manager database.

• Back up the HP P6000 Replication Solutions Manager database. It contains managed set andjob information that you can restore on another management server if necessary.

• Practice the recovery plan. Ensure that everyone in your storage administration is preparedfor disaster recovery. Practice different failure scenarios and make decisions ahead of time.For example, if a controller fails, is it more important not to disrupt processing by doing aplanned failover, or not to be at risk for a second controller failure that requires an unplannedfailover? In the case of multiple sites, which site has precedence for troubleshooting? Simulateddisaster recoveries are a good way to verify that your records are up-to-date and that allrequired patches are installed.

Failover and recovery proceduresThe failover procedure depends on the severity of the failure or the reason for the failover. Forexample, the procedure for a planned failover applies to anticipated power disruptions, scheduledequipment maintenance at the local site, or a need to transfer operations to another array. Anotherprocedure applies to unplanned events such as multiple controller failures, multiple host failures,or an unplanned power outage at the local site.You may decide not to fail over in some situations. For example, if only one component fails, youcan repair that component and avoid failing over an entire DR group. In the event of a data centerfailure, or if you are planning downtime with a local array, failing over to the remote array canensure minimal interruption of data access.

IMPORTANT: Always verify that all components of the remote array are 100% operationalbefore you fail over.

NOTE: HP recommends that you not fail over any DR group more than once every 15 minutes.

Planning for a disaster 103

Performing failover and recoveryFailover and recovery procedures include such actions as failover, suspend, resume, disable failsafe,mounting, and unmounting. You can perform these actions using the following interfaces and tools:

• HP P6000 Replication Solutions Manager GUI

• HP P6000 Replication Solutions Manager CLI

• HP P6000 Replication Solutions Manager jobs

• HP Storage System Scripting Utility

• HP P6000 Command ViewFor specific procedures, see the interface documentation.

Choosing a failover procedureTable 5 (page 105) summarizes situations that require a failover and those that do not. Eachrecommended action corresponds to a procedure documented later in this chapter. Becausereplication can be bidirectional, your array may be a source and a destination for separate DRgroups. Use this table to customize contingency plans for your environment.


Table 5 When to fail over a DR group, managed set, or array

Recommended HP P6000 Continuous Access actionFailure situation

DR group in failsafe modeDR group in normal mode

Perform a planned failover on the destination array. See “Planned failover” (page 105).Maintenance preventing access tosource array

Manually intervene to fail over data on destination array, and then restart processingat the destination array. Perform an unplanned failover. See “Unplanned failover”(page 108).

Total loss of source array

Loss of both source controllers

NoneLoss of single source controller

Manually intervene to continue processingat the source array. See “Recover from

NoneTotal destination array loss

Loss of both destination controllers failsafe-locked after destination loss”(page 108).

Loss of all ISLs

Investigate to determine the reason for the outage and if appropriate manually interveneto fail over data on the destination array, and then restart processing at the destinationarray. Perform an unplanned failover. See “Unplanned failover” (page 108).

Loss of SAN connectivity from the serverto the source array

NoneLoss of single source intersite switch

Manually intervene to fail over data to the destination array, and then restart processingat the destination array. Perform an unplanned failover. See “Unplanned failover”(page 108).

Extended power outage at primary site

Failover not necessary. Browse to standby managing server.Loss of managing server

NoneLoss of a single disk in redundantstorage

NoneLoss of single host of cluster

Failover may not be necessary. Any data generated is being replicated to the destinationarray. If the virtual disk fails completely then fail over to the destination. See “Disk grouphardware failure on the source array ” (page 114).

Disk group hardware failure (loss ofredundancy) on the source array

Failover not necessary. See “Disk group hardware failure on the destination array”(page 115).

Disk group hardware failure (loss ofredundancy) on the destination array

Planned failoverScenario: Due to scheduled maintenance at the local site, you need to move operations from thelocal array to the remote array.Action summary: Stop processing in the local data center and allow any data in the write historylog to drain, and then begin the failover. When the failover is complete, you can continue tooperate from the new source and enable failsafe mode if desired. When the planned maintenanceis complete, you can fail back to the original source (this is another planned failover event).Figure 54 (page 106) shows a planned transfer of operations to a remote site.

Failover and recovery procedures 105

Figure 54 Planned and unplanned failover

TIP: With HP P6000 Replication Solutions Manager, you can designate a Home DR group toidentify the preferred source. By default, the source at the time the DR group is created is Home.As the role of the array changes after multiple failover and failback events, the Home designationpersists.


Planned Failover ProcedureTo execute a planned failover:1. Optionally, move storage management to another management server. For instructions, see

the HP P6000 Command View User Guide.2. Ensure that all DR groups have resumed and are fully normalized.

Check the DR group status using HP P6000 Command View or HP P6000 Replication SolutionsManager. If a DR group is merging or a normalization is in progress, wait for the process tocomplete.

3. If the write mode is currently set to asynchronous, set it to synchronous.If you are running XCS 6.000 or later, consider the following:

• You must wait for the log to merge after changing the write mode to synchronous andthen verify that the actual write mode has changed to synchronous.

• Transitioning to synchronous write mode will impact server I/O performance. Forenvironments running in asynchronous mode on XCS 6.000 or later, it is best to halt allserver processing while data in the write history log is draining, as server I/Os will betreated in a synchronous replication manner, resulting in a severe performance impacton server write I/Os.

• When performing a planned site failover, you must put DR groups in synchronous modebefore performing the actual failover activity. Omitting this mode change before performingthe site failover results in performing an unplanned site failover (and the resultingnormalization). Once the site failover has finished, you can change the replication modeback to asynchronous mode again.

• If the intersite link (or links) are broken and the DR group (or groups) has entered loggingbut has not yet been marked as a normalization (as occurs when the log reaches 100%capacity), a link is re-established and a log merge should be performed before the failoveris performed.

• If the source site requires maintenance, put the DR groups into synchronous mode, waitfor the write history logs to drain, and perform the failover. Once failover occurs, suspendreplication and the destination array will start logging. When the primary array returns,re-establish a HP P6000 Continuous Access link, and take one of the following actions:

◦ Wait for the log to drain.

◦ Invalidate the log and start a normalization.

4. Properly halt all applications, and then shut down the servers. Ensure that the server hasproperly flushed all internally cached data. Failure to do this will result in the loss of datacached on the server.

5. Fail over the DR groups.6. Issue operating system commands for resuming host I/O to the new source disks. For

operating-system specifics, see “Resuming host I/O after failover” (page 118).7. If you plan to operate for an extended time at the remote site, you can change the write mode

to asynchronous after the original primary array is back up and running.a. If the DR group is currently suspended, resume it and wait for log to finish merging.b. Once the log has finished merging, set the write mode to asynchronous.

NOTE: Remember to set the write mode back to synchronous and allow the write historylog to completely drain before you fail back to the original source.


8. If you plan to operate for an extended time at the remote site and need to enable failsafemode on a DR group. Make sure the new destination (previous source) and Fibre Channellinks are functioning, and then perform the following steps:a. If the DR group is suspended, resume it and wait for the log disk to finish merging.b. Once the log has finished merging, change the DR group to failsafe mode.

NOTE: You can enable failsafe mode at the destination array during a merge ornormalization.

After resolving the cause of a failover, you have three options:

• Remain failed over on the remote array.

• Return operations to the local array. See “Failback to the original source following a plannedor unplanned failover” (page 110).

• Return operations to new hardware at the local site.

Unplanned failoverScenario: You have experienced an unplanned loss of the local site or the source array. The durationof the outage is unknown. The hardware components (for example, hosts, array controllers, andswitches) at the local site may or may not still remain intact.Action summary: Fail over the destination DR array. When the local site is back online, you canfail back to the previous source array or to a replacement array. Figure 54 (page 106) shows anunplanned transfer of operations to a remote site.When an unplanned site failover occurs when the DR group is in asynchronous mode, the DRgroup is put in synchronous mode and a normalization is initiated when the destination arraybecomes available. The replication mode returns to asynchronous mode once the normalizationcompletes.Procedure:To resolve an unplanned failover:1. If you cannot access the management server that is managing the arrays, establish management

control with another management server. For instructions, see the HP P6000 Command ViewUser Guide.

2. Fail over the DR groups.Using the HP P6000 Replication Solutions Manager, select the destination DR group, andthen select Actions→Failover. See the online help for additional information.

3. Issue operating system commands to resume host I/O to the new source. See “Resuming hostI/O after failover” (page 118).

After resolving the cause of a failover, you have three options:

• Remain failed over on the remote array.

• Return operations to the local array. See “Failback to the original source following a plannedor unplanned failover” (page 110).

• Return operations to a replacement array at the local site.

Recover from failsafe-locked after destination lossScenario: You have experienced an unplanned loss of the remote array or a loss of the connectionto the remote array, due to failure of the ISLs, loss of power at the remote site, loss of remoteswitches, and other similar events. The duration of the outage is unknown. The DR groups arefailsafe-locked and host I/O is paused.


Action summary: Change from failsafe-enabled mode to normal mode and resume host I/O untilthe connection to the remote array is re-established. When the connection is stable, change backto failsafe-enabled mode. Figure 55 (page 109) illustrates the steps required to resume operationsif you cannot access the destination while in a failsafe-locked state.

Figure 55 Resumption of operation if unable to access destination in failsafe mode


Procedure:To resume operation if you are unable to access the destination in failsafe mode:1. Change affected DR groups from failsafe-enabled mode to normal mode.2. If necessary, issue operating system commands to the local hosts to restart I/O on the virtual

disks that were failsafe-locked. See “Resuming host I/O after failover” (page 118).3. When connections to the destination are re-established, control the merging of data at the

destination by suspending replication on the less important DR groups. This forces the controllersto replicate the most important data first when the links to the destination are re-established.For more information, see “Throttling a merge I/O after logging” (page 124).

NOTE:If DR groups are suspended for an extended amount of time, the log can run out of space.Restoring the connection to the destination array initiates a normalization of these DR groups.During the normalization operation, the data is inconsistent at the destination.

4. When merging is complete, change DR groups from normal mode to failsafe-enabled mode,if desired.

NOTE: Once a DR group starts a normalization, you can enable failsafe mode for that DR group.

Failback to the original source following a planned or unplanned failoverScenario: You are operating from an array that is not the original source (it's not designated as“Home” in HP P6000 Replication Solutions Manager). You need to move operations from thedestination array back to the source array.Action summary: Prepare the source array for the failover and fail over the DR group. Failback(also known as reverting to Home) is identical to a planned failover. Fifteen minutes after failingover from a source to a destination array, you can fail back in the other direction.Procedure:To fail back to the original source:1. If desired, move storage management to another management server. For instructions, see

the HP P6000 Command View User Guide.2. Properly shut down all applications, and then shut down the servers. Ensure the server has

properly flushed all internally cached data. Failure to do this will result in a loss of data cachedon the server.

3. Ensure that all DR groups have resumed and are fully normalized or merged. If a DR groupis merging or a normalization is in progress, wait for the process to complete.

4. Fail over the DR groups (or revert to Home using HP P6000 Replication Solutions Manager).5. Issue operating system commands to resume I/O to the new (original) source. See “Resuming

host I/O after failover” (page 118).

Return operations to new hardware

NOTE: This section assumes a failure of the array hardware only and does not provide informationfor recovering from a site disaster that includes the failure and replacement of other hardware suchas servers.

Scenario: Some type of disaster damaged local equipment and forced a failover to a remote site.Hardware on the local source array was replaced. The new hardware now acts as the destinationarray; you are operating from an array that is not the original source (designated as Home).Action summary: When the site is back online, fail over to new hardware at the local site.Figure 56 (page 111) illustrates the steps to return operations to new hardware.


Figure 56 Returning operations to replaced hardware

Procedure:This procedure does not include steps for rebuilding servers (this should be part of your disasterplan). For more information about the steps in this procedure, see the online help for HP P6000Command View or HP P6000 Replication Solutions Manager.


Table 6 Sample array log

Current source arrayArray with failed or new hardware

Array name

Array name

Array name

Array name

Array name

Array name

Array name

Array name

1. Record the name of the array with failed or new hardware (current destination) and the nameof the current source array in a log such as the one shown in Table 6 (page 112). For example,the array with new hardware is named HSV01 and the current source array is named HSV02.Refer to this table during the procedure as needed.

2. If running controller software versions prior to 6.1xx on the current source array, resume allDR groups.

3. Delete all DR groups that have had a relationship with the failed hardware.4. Install the replacement array and configure as necessary (for example, disk groups)5. Re-establish communication between the source and new destination arrays. Add the new

array to the SAN, enable the ISLs, or place the arrays into the same zone.6. Perform one of the following:

• If the replaced array configuration was captured with HP Storage System Scripting Utility(called the utility), execute the script ConfigName_step1A on the new hardware, andthen proceed to Step 11. See the HP Storage System Scripting Utility Reference forinstructions. ConfigName is a user-assigned name given to the utility script at the timeof creation. See “Backing up replication configuration” (page 126).

• If you are not using a utility script for recovery, initialize the repaired or replaced arrayusing the information you recorded in Table 6 (page 112). See the HP P6000 CommandView User Guide for initialization instructions.

NOTE: To preserve existing zoning, assign the new hardware the WWNs of the failedhardware.

7. Add the disk groups on the new hardware.8. Add the hosts for the system with new hardware.9. Create the non-DR group virtual disks.10. Present all non-DR group virtual disks to their hosts.11. Perform one of the following:

• If the source array configuration was captured with the utility, executeConfigName_step2 on the source array. ConfigName is a user-assigned name givento the utility script at the time of creation. DR groups are re-created with the utility if theywere performing as the source when the configuration was captured. This step may takesome time to complete.This action includes the following assumptions:

◦ The new array has the same type of hardware as the array that failed.

◦ All host WWNs are still the same.


You also have to take into account that the DR groups may have changed membership(or new ones have been created) since the time the original source array was destroyed.

• If you are not using a utility script for recovery, re-create all DR groups on the sourcearray using the information recorded in “Configuration form ” (page 126). Specify thereplaced array for the destination.

12. If you used the utility to re-create DR groups on the source array, you must manually re-createany DR groups that had their source on the failed hardware. The utility will not re-create theDR groups on the source array if they performed as the destination when the configurationwas captured. After you perform this step, all DR groups reside on the source array.

13. If desired, set all affected DR groups from normal mode to failsafe-enabled mode.14. Perform one of the following:

• If the original array configuration was captured with the utility, executeConfigName_step3 on the new hardware. ConfigName is a user-assigned namegiven to the utility script at the time of creation.

• If you are not using a utility script for recovery, present the destination virtual disks on thearray with new hardware to the appropriate hosts using the information you recorded inTable 8 (page 126).

15. If you used the utility to present destination virtual disks to their hosts, you must manuallypresent any additional virtual disks that originally had their sources on the failed hardwareto their hosts on the array with new hardware. The utility will not present virtual disks whosedestination was the current source array when the configuration was captured. After performingthis step, all destination virtual disks are presented to hosts.

16. If the replaced array is to be the source for the DR groups, fail over any DR groups. See“Planned failover” (page 105).

17. Issue operating system commands to restart host I/O on the source array. For more information,see “Resuming host I/O after failover” (page 118).

18. (Optional) Set the DR groups to the desired Home setting.

Recovering from a disk group hardware failureDisk group hardware failure occurs when a Vraid cannot be used because there are too manyHDD failures in a disk group. The failure results in an inoperative disk group. This condition is theresult of the loss of one disk for Vraid0, or the loss of two disks for Vraid1 and Vraid5. In eachcase, the hardware must be replaced and the disk group data rebuilt. (For a complete descriptionof disk group failures, see the HP Enterprise Virtual Array Configuration Best Practices White Paperfor your array model.) This section describes the symptoms and recovery of an inoperative diskgroup at either the source or destination array.If an array has only one disk group and that disk group fails, the array becomes inoperative. Tomanage the array, you must reinitialize it.Follow the procedure “Disk group hardware failure on the source array ” (page 114) or “Disk grouphardware failure on the destination array” (page 115).

Failed disk group hardware indicatorsIf disk group hardware fails, HP P6000 Replication Solutions Manager displays the icons describedin Table 7 (page 114).


Table 7 HP P6000 Replication Solutions Manager display icons

DescriptionIconResource

Indicates that the array is in an abnormal stateand requires attention.

Array

Indicates a catastrophic failure and requiresimmediate action.

Virtual disks

Red indicates a failure; yellow indicates that theDR group is in a degraded state. Either conditionrequires immediate attention.

DR groups

Disk group hardware failure on the source arrayScenario: A hardware failure on a source array causes a DR group to become inoperative.

NOTE: The operational state of the DR group at the source array will show as Failed ( );

on the destination array the DR group will show as Good ( ).

Action summary: If you plan to recover using data on the destination array, then fail over thedestination array (unplanned failover) and delete DR groups and virtual disks on the failed array.Repair the failed disk group. Re-create DR groups, virtual disks, and host presentations. If the failedsource array was logging at the time of the hardware failure, you must recover using data at thedestination array (if you are running HP P6000 Continuous Access) or using a backup.There are two ways to recover from a disk group hardware failure on the source array:

• If data replication was occurring synchronously when the source disk group became inoperative,the data at the destination array is current and I/O consistent. Fail over on the destinationarray after performing the proper resolution process at the failed array as described in thefollowing procedure. Repair the inoperative disk group and re-create the DR groups. Copydata from the destination array to the repaired source.

• If your disk group becomes inoperative when the DR groups are logging or while in enhancedasynchronous write mode, the data is not current, but still I/O consistent on the destinationarray. Stale data is not as current as the data on the source array. If you prefer to use staledata for recovery, the steps are the same as if replication were occurring normally.

Procedure:Perform the following steps when a disk group hardware failure occurs on the source array andthe data on the destination array is current:1. Check to determine if the DR groups were logging or merging.2. From HP P6000 Command View, navigate to each DR group on the destination array and

fail over, if possible, if immediate access to the data is required. See “Unplanned failover”(page 108)).

3. Using HP P6000 Command View to manage the failed (previous source) array, navigate tothe failed disk group.A list of failed virtual disks and DR groups is displayed.


Figure 57 Disk Group Hardware Failure window

4. Click Start Resolution Process.After a prompt for confirmation, a list of failed DR groups is displayed.

5. One at a time, select the affected DR groups and click Delete, then OK to confirm the deletion.Deleting a DR group removes the relationship between the virtual disk members; it does notdelete data from the virtual disks as they remain intact on source and destination systems.

6. If the failover has not occurred, use HP P6000 Command View to navigate to each DR groupon the destination array and fail over if possible. See “Unplanned failover” (page 108).Once a DR group is failed over, the DR group will be deleted automatically. If failover occurredduring Step 2, the DR group must be deleted manually.

7. (Optional) Repair your hard drives on the failed array. Delete the virtual disks which werepart of the original source DR group.For more information, see the EVA User Guide for your array model and the HP P6000Command View Software Suite User Guide.

8. Refresh the new source array and re-create the DR groups.9. After normalization occurs between the source and destination arrays, fail over the DR groups

using the procedure in “Planned failover” (page 105).

Disk group hardware failure on the destination arrayA hardware failure on a destination array causes the DR group to become inoperative.Action summary: Delete the DR groups on the source array that replicated to the failed disk group,repair the failed disk group on the destination array, re-create your DR groups on the source array,and make host presentations at the destination array.


Your first indication that a disk group has become inoperative may be icons like those shown in“HP P6000 Replication Solutions Manager display icons” (page 114), except that the destinationdisk group status is Unknown.

NOTE: When you delete DR groups to recover from a disk group hardware failure, you do nothave disaster tolerance until you re-create the DR groups and they have completed normalization.If you create mirrorclones of the destination virtual disks in the DR group and regularly updatethem, you will have some protection from a disaster but the data will be as old as the last mirrorcloneresynchronization.

Procedure:Perform this procedure when a disk group hardware failure occurs on the destination array.

NOTE: Because the source data is intact, there is no data loss in this scenario.

1. Disable failsafe mode, if set.2. Use HP P6000 Command View to navigate to the failed disk group.

A list of failed virtual disks and DR groups is displayed. See Figure 57 (page 115).3. Click Start Resolution Process.

After a confirmation message, a list of failed DR groups appears.4. Unpresent the affected destination virtual disk members: one at a time, select an affected

virtual disk, select the Presentation tab on the Vdisk Properties window; and then clickUnpresent.Repeat this step for each affected destination virtual disk member.

5. Select an affected DR group, and then click Delete.Deleting a DR group removes the relationship between the virtual disk members; it does notdelete data from the virtual disks.

6. Repeat Step 5 for each affected DR group.7. Navigate to the disk group and click Finish to resolve the disk group hardware failure.8. On the source array, delete the DR group associated with the DR groups deleted in Step 5.9. (Optional) Repair your hard drives and re-create your disk group on the destination array.

For more information, see the user guide for your array model and the HP P6000 CommandView User Guide.

10. Refresh the source array and re-create the DR groups.11. On the destination array, present the destination virtual disks.

Protecting data from a site failureWhen the destination array is unavailable and both controllers on the source array are restarted,host presentation of source virtual disks is blocked and remains blocked until the destination arraybecomes available (and can communicate with the source array) or until you suspend the DR group.It is possible to disable this feature on newer versions on controller software. For more information,see “Failsafe on Link-down/Power-up” (page 11).Blocking host presentation protects data during a site failure, where the potential exists for bothsides of the remote replication connection to be presented to hosts simultaneously. Blocking alsoprotects cluster members from detecting or accessing two copies of the same data. It also protectsboot from SAN (BFS) servers from two hosts booting against the same boot image.You can use HP P6000 Replication Solutions Manager or HP P6000 Command View to determineif host presentation is blocked.


In HP P6000 Replication Solutions Manager:

• On the General tab of the Virtual Disk Properties window, BLOCKED appears in the OperationalState box.

• On the General tab of the selected DR group window, BLOCKED appears in the OperationalState box.

In HP P6000 Command View:

• On the Vdisk Properties window, None (DR members protected) appears in the hostaccess box.

• On the DR Group Properties window, Blocked appears in the Group host access box.To remove the host presentation block, suspend replication or repair the connection to the destinationarray.

Protecting data from a site failure 117

8 Operating system proceduresThis chapter describes operating system procedures that accompany remote replication procedures,especially for failover and recovery.

Resuming host I/O after failoverProcedures for detecting disk devices and restarting I/O operations after DR group failover differamong operating systems.

HP OpenVMS• If the remote hosts are shut down, boot them now.

Booting the hosts enables OpenVMS to recognize the drives.

• If the remote hosts are not shut down, issue the following command from a privileged accountto enable OpenVMS to recognize the drives:MCR SYSMAN IO AUTOCONFIGURE/LOG

HP Tru64 UNIX• If the remote hosts are shut down, boot them now.

Booting the hosts enables Tru64 UNIX to recognize the drives.

• If the remote hosts are not shut down, use the following command to recognize the drives:hwmgr –scan scsi

This may take a while for large configurations, in which case, scan only the SCSI buses thathave added units, scanning only one bus at a time using the following command where x isthe SCSI bus number:hwmgr –scan scsi –bus x

HP-UXTo resume I/O in HP-UX:1. Do one of the following:

• If the remote hosts are shut down, boot them now.Booting the hosts enables HP-UX to recognize the drives.

• If the remote hosts are running, issue the # ioscan -fncdisk command to scan fornew devices.

2. If the device special files are not present, issue the # insf -e command to add the specialfiles.A subsequent ioscan will return the devices with the special files.a. When the remote hosts are running (and the disks and special files are present), you must

create folders for the new vgxx devices. Create the initial directory using the mkdircommand, and then create the special file using the mknod command:# mkdir <volumeGroupName>

# mknod <volumeGroupName> group c 64 minor#

Example:# mkdir /dev/vg09

118 Operating system procedures

# mknod /dev/vg09/group c 64 0x090000

b. After the folders are created, the disks appear, and the special files are present, use thevgimport command to create the virtual group:# vgimport <volumeGroupName> <deviceSpecialFiles>

Example:# vgimport /dev/vg09 /dev/dsk/c18t0d /dev/dsk/c18t1d0/dev/dsk/c25t0d0

c. To display this virtual group using # vgdisplay -v /dev/vg09. If a Volume groupnot activated error is displayed, you must activate the volume group using thevgchange command:# vgchange -a y <volumeGroupName>

Example:# vgchange -a y /dev/vg09

d. If you encounter errors while trying to mount the failed over volume (such as an errorindicating the volume is corrupt), run a file system check. This is fairly typical as the filesystem may not have been dismounted properly. You can repair the device using thefsck command:# fsck <logicalVolumeName>

When the devices are error-free, they can be mounted.

NOTE: The <volumeGroupName> is the name of the volume group you originallycreated at the local site.The deviceSpecialFiles are from the ioscan in the form /dev/dsk/c_t_d/.For consistency, configure the deviceSpecialFiles for the failed over LUNs at theremote site with the same volume groups, logical volumes, and file systems as the LUNsat the local site.

IBM AIX• If the remote hosts are shut down, boot them now.

Booting the hosts enables AIX to recognize the drives.

• If the remote hosts are running, use the following commands to recognize the drives and verifythat they are present:cfgmgr –v

lsdev –Cc <disk>

Use the following commands to access file systems on the failed–over virtual disks:importvg –y <volumeGroupName> hdiskx

mount all

NOTE: The <volumeGroupName> is the name of the volume group you created at the localsite, and x is the number of the hdisk assigned to the failed over virtual disk. If the –y<volumeGroupName> parameter is omitted, AIX creates a default volume group name (forexample, vg00).

LinuxTo resume I/O in Linux:

Resuming host I/O after failover 119

1. Reboot the servers at the remote site.2. Remount the file system.For more information, see “Bootless failover using LVM with Linux ” (page 122).

Novell NetWare• If the remote hosts are shut down, boot them now. If you are using traditional NetWare

volumes, booting the hosts allows NetWare to recognize the drives and automatically mountthe volumes. If you are using NSS logical volumes, booting the hosts allows NetWare torecognize the NSS pools and activate them. However, you must manually mount each NSSvolume by issuing the MOUNT VolumeName command from the NetWare console.

• If the remote hosts are running, but they do not recognize the drives, issue the followingcommand from the console before mounting the volumes:SCAN FOR NEW DEVICES

Alternative procedure:1. Use the NWCONFIG utility to issue this same command.2. Mount the volumes using the following commands:

MOUNT ALL (for traditional NetWare volumes)MOUNT <VolumeName> (for NSS logical volumes)

Sun SolarisReboot the remote hosts using the reboot –– –r command, or use the following version-dependentcommands to update the HP Secure Path Manager:

• For Solaris 6, 7, and 8:drvconfig –v

disks

/opt/CPQswsp/bin/spmgr display

• For Solaris 9:Present new units with sequential LUNs, following the existing LUNs.1.

2. Run the following command:devfsadm –C

Or, if you are using HP Secure Path:/opt/CPQswsp/bin/spmgr display

If HP Secure Path was not configured for these units, use the following version-dependent commandsto add them to the HP Secure Path Manager:

• For Solaris 2.6, 7, and 8:/opt/CPQswsp/bin/spconfig

/opt/CPQswsp/bin/spmgr/display –u

/opt/CPQswsp/bin/spmgr add <WWLUNID>

devfsadm –C

/opt/CPQswsp/bin/spmgr display

• For Solaris 9:1. Add the units using spmgr add <WWLUNID> or spmgr add–r WWNN all.2. Run update_drv –f sd to inform the system about attribute changes to the sd driver.3. Run devfsadm –C to create /dev entries for the new units.


If you are using MPIO, and it has not been configured for these devices:1. Issue the cfgadm command.

# cfgadm –al –o show_FCP_dev

Output:c3 fc-private connected unconfigured unknown

c3::210000e08b0a5b65 unknown connected unconfigured unknown

c3::500060e802eb2b0b,0 disk connected unconfigured unknown

c4 fc-private connected unconfigured unknown

c4::210100e08b2a5b65 unknown connected unconfigured unknown

c4::500060e802eb2b14,0 disk connected unconfigured unknown

2. Run the cfgadm command for each EVA port on the storage array.Example:# cfgadm –c configure c3::500060e802eb2b0b

# cfgadm –c configure c4::500060e802eb2b14

NOTE: The controller instance (c#) may differ between systems.

3. Take one of the following actions:If you are using Solaris 9:a. Update the sd driver:

#update_drv –f sd

b. Issue the devfsadm command to build the appropriate device files:#devfsadm –C

If you are using Solaris 2.6, 7, or 8, reboot the host to finish configuring the new devices:# reboot – –r

You can now view the drives using the format command. For more information, see the currentversion of the multipath driver documentation, located at http://www.sun.com/storage/san.

• If you are using a volume manager application, import the volume groups. See your volumemanager documentation.

• You may need to issue the fsck command to repair any devices that were dismountedimproperly.

VMwarePerform this procedure as root user from the VMware server console:1. Click Storage Management on the Options tab.2. Click Rescan SAN, and then click Refresh.

New devices are listed on the Disks and LUNs window.

Alternatively, you can issue the following command from the VMware server command shell, wherehba adapter is the VMware adapter on the SAN:cos-rescan.sh <hba adapter>

WindowsTo resume I/O in Windows:

Resuming host I/O after failover 121

http://www.sun.com/storage/san

1. On each host, log on to an account that has administrative privileges.2. Select Programs > Administrative Tools > Computer Management.3. Click Disk Management.4. After Disk Management has initialized, select Actions > Rescan Disks. If the units fail to appear,

press F5 (Refresh).All of the failed over units are displayed in the right pane.

Red Hat and SUSE Linux LifeKeeper clustersRed Hat Linux and SUSE Linux LifeKeeper clusters must be zoned so that clustered hosts can seeonly one controller port per fabric. The operating system host mode of the controller must be setto Linux.

Bootless failover using LVM with LinuxThis section describes how to perform a bootless DR group failover using Logical Volume Manager(LVM) with Linux. The section includes separate procedures for standalone LVM and LVM withclusters (SUSE SLES 8 running LifeKeeper 4.4.3). Perform the procedures for the source host, andthen perform the procedures for the destination host.

NOTE:• These procedures are not valid for unplanned failovers.

• The term bootless means that after the LUNs are first presented to a destination host (whichrequires an initial reboot), no additional reboot of that host is required.

Source host procedureUse one of the following procedures to perform a bootless DR group failover on the source host.If you are not running LifeKeeper:1. From the source host, stop I/O to the LUNs.

Allow enough time for the I/O to complete before proceeding to the next step.2. Unmount the volumes in the DR group.

Example: unmount /mounts/lvol1

3. Change the status of the LUNs to inactive using the vgchange <volumeGroupName> –an command.Example: vgchange vg01 –a n

4. Make the group unknown to the system using the vgexport command.Example: vgexport vg01

5. Perform a failover of the DR group.6. Depending on the number of LUNs, take one of the following actions to prevent HP Secure

Path from detecting a failed disk:• For individual LUNs, run spmgr quiesce –p path for each path visible to the LUNs.

• For all LUNs at once, run spmgr set –p off to turn off path verification for all LUNsvisible to the system.

If you are running LifeKeeper 4.4.3 clusters:1. Take your resources out of service with LifeKeeper.2. From the system console:

a. Issue the mount command to verify that the volume is unmounted.b. Issue the vgscan command to verify that the volume group is exported.


3. Perform a failover of the DR group.4. Depending on the number of LUNs, do one of the following to prevent HP Secure Path from

detecting a failed disk:• For individual LUNs, run spmgr quiesce –p path for each path visible to the LUNs.

• For all LUNs at once, run spmgr set –p off to turn off path verification for all LUNsvisible to the system.

Destination host procedureIf this is the first time that LUNs are being presented to the destination host, reboot the host to detectthe new LUNs. If a reboot is not required (LUNs have already been presented) and the paths arequiesced, issue the spmgr restart all command to un-quiesce the paths.Use one of the following procedures to perform a bootless DR group failover on the destinationhost.If you are not running LifeKeeper:1. Issue the vgimport <volumeGroupName> <physicalVolumePath> command to make

the volume known to the system.Example: vgimport vg01 /dev/sda1

2. Change the status of the LUNs to inactive using the vgchange <volumeGroupName> –ay command.Example: vgchange vg01 –a y

3. Mount the file systems.Example: mount –t reiserfs /dev/vg01/lvol1 /mounts/lvol1

4. Start host I/O.5. If the verification path is turned off, issue the spmgr set –p on command.If you are running LifeKeeper 4.4.3 clusters:1. If this is the first time LUNs are being presented to the destination host, you must build the

resource hierarchies for each LUN. See the documentation on the LifeKeeper CD.2. Using the LifeKeeper GUI, take your resources out of service.3. Start host I/O.4. If the verification path is turned off, issue the spmgr set –p on command.

Bootless failover using LVM with Linux 123

9 Managing remote replicationThis chapter describes routine and advanced procedures for managing remote replication.

Using remote replication in a mixed array environmentThe remote replication features that are available depend on the controller software version. Thefollowing rules apply to remote replication between an array with XCS controller software and anarray with VCS controller software:

• If a feature such as the supported number of virtual disks in a DR group is supported differentlyin the source and destination arrays, the more restrictive value applies to the source-destinationpair.

• If a feature such as enhanced asynchronous write mode is not available in either array, itcannot be used in a source-destination pair.

For version-specific features and current support limits, see the HP P6000 Enterprise Virtual ArrayCompatibility Reference.

Managing merges and normalizationWhen logging occurs in synchronous write mode or basic asynchronous write mode, there isdisparity between data being processed at the local site and data at the remote site. A merge ornormalization corrects this disparity when the cause for the interruption is remedied.

• A merge sends data from the log disk in write order so the destination copy remains crashconsistent.

• A normalization copies data in 1-MB chunks from the source virtual disk to the destinationvirtual disk, and data is inconsistent until the normalization is complete.

Throttling a merge I/O after loggingThrottling is the channeling of I/O to merge critical data first by suspending and then resumingspecific DR groups.When replication has been halted, data is logged on the source array (except when failsafe isenabled). When replication is resumed, if there are several DR groups with large logs, they maycompete for bandwidth if they try to merge simultaneously. By resuming critical DR groups first,the controllers merge only the most critical data first, allowing this data to be synchronized andbecome accessible before the less important DR group data. As the more important DR groupsfinish merging, you can resume the replication of DR groups that were left suspended.

Maintaining I/O performance while mergingDuring a merge, the controller software manages merge writes and host I/O, allowing one newhost I/O into the write history log for every two I/Os merged out of the write history log to thedestination array. This ratio ensures that the log empties faster than it fills. If host performance isan issue during merging, you can postpone merging to a period of low demand by using thesuspend command to prevent merging and then using the resume command to allow merging.VCS 6.0 or later uses this same ratio to empty the log when it receives a request to change thewrite mode from enhanced asynchronous to synchronous.

Preparing for a normalization

IMPORTANT: An HP P6000 Business Copy license is required for this procedure.

When a DR group write history log is marked for a normalization, there is a risk to the destinationcopy once the process begins. You can eliminate this risk by using the HP P6000 Business Copy

124 Managing remote replication

snapshot, mirrorclone, or snapclone feature to create a copy of the destination virtual disk beforea normalization starts. If a major failure occurs at the local site during a normalization, HP P6000Business Copy can provide a clean copy of data as it existed before normalization writes startedon the remote array. (Note that any new writes that occurred on the source between the time thecopy was created and the major failure occurred are lost.)It is recommended that you use the HP P6000 Business Copy mirrorclone feature if supported onyour XCS version, or a fully allocated snapshot if your XCS version supports instant restore fromsnapshot. If neither mirrorclone nor snapshot is available, use the HP P6000 Business Copysnapclone feature. As a best practice, whenever a link is expected to be down more than severalminutes, create a copy of the destination virtual disk.Some versions of controller software support instant restore of a snapshot of a mirrorclone to themirrorclone parent. When a DR group source member is instantly restored from a snapshot (eitherits own snapshot or the snapshot of an attached mirrorclone), the group will use the available bitmap to copy only blocks that have changed, rather than the entire content of the DR group. Thisis more efficient than performing a full copy of the data and is referred to as a “fast copy”.The fast copy functionality is only associated with the source DR group member. The bit map usedfor the fast copy is only stored on the source DR group member's array. The bit map is not availableon the destination DR group member’s array, so an asynchronous DR group cannot initiate a fastcopy after a failover. A full copy is required to ensure the data on the new source is copied to thenew destination. The new source will create and maintain a bit map for fast copy should acommunication failure or group suspend occur. See the HP P6000 Enterprise Virtual ArrayCompatibility Reference to determine if your array controller software supports this feature.

NOTE: You cannot use these procedures if a normalization is already in process.

1. Navigate to each affected DR group and suspend replication.2. Make a snapclone of the destination virtual disk using the procedures described in the

application's online help. On versions of XCS controller software that supportreverse-resynchronization, HP recommends using mirrorclones or fully allocated snapshots.

3. Use HP P6000 Replication Solutions Manager to navigate to each affected DR group andresume replication. Replication will resume when the links are restored.

NOTE: A DR group must be suspended to perform an instant restore from a mirrorclone, asnapshot of a mirrorclone, or a snapshot of a virtual disk.

Optimizing performanceThe following information describes how you can improve performance when using HP P6000Continuous Access.

Load balancing

NOTE: The following recommendations provide a fully redundant solution that will survive an ISLfailure and continue to provide full bandwidth performance.

For best performance of remote replication, the average workload (reads and writes) should beequal on both controllers and on both fabrics and ISLs. To obtain this balance, take measurementsand keep the utilization rate of each ISL below 40 percent. If one link fails, the average utilizationof the operating link should not exceed 80 percent. Similarly, the utilization rate of a single controlleras measured on all host ports should not exceed 45 percent on average, or peak above 50 percent,to prevent overloading the surviving controller should one controller fail.In general, let the hosts manage I/O load balancing. Remember, all members of a DR group mustshare a preferred controller, therefore load balancing a single application with all of its virtualdisks in a single DR group (as required) across multiple controllers is not possible.

Optimizing performance 125

Backing up replication configurationHP recommends regular backups of replication configurations and jobs. Current backups areessential to successful disaster recovery. You can also use backups to duplicate the localconfiguration and jobs on remote and standby management servers and keep those servers current.You can use HP P6000 Replication Solutions Manager and HP Storage System Scripting Utilityto make backups, or you can back up your configuration manually.

Using HP P6000 Replication Solutions Manager for backupsThe export feature of HP P6000 Replication Solutions Manager copies the replication database,including DR groups, jobs, and the encrypted HP P6000 Command View (Storage Agent) password.You can import the export file to restore the database or to duplicate the database on anothermanagement server. See the HP P6000 Replication Solutions Manager Administrator Guide forexport and import procedures.

IMPORTANT: If the password for the HP P6000 Command View instance on the remote orstandby server is different from the password imported with the local HP P6000 Replication SolutionsManager database, all storage resources on the remote management server are displayed in anunknown state. You must change the imported replication manager HP P6000 Command View(Storage Agent) password to match the resident HP P6000 Command View password, or changethe password of the resident HP P6000 Command View instance to match the imported password.

Using HP Storage System Scripting Utility to capture your configurationThe HP Storage System Scripting Utility Capture Configuration command copies informationabout the array and DR group configuration to the console or a user-specified file. You can usethis output to re-create the configuration after a hardware failure. For more information aboutsaving and restoring configuration information, see the HP Storage System Scripting Utility Reference.

Keeping a written record of your configurationYou should keep a written copy of your configuration information. Use the form shown inTable 8 (page 126) as a guideline for capturing information.Record the WWN of each host HBA, array controller, and management server on the local andremote sites. The WWN is a hexadecimal number on the bottom of the HBA board. Look for asmall barcode label with an IEEE precursor (for example, IEEE 1000–0000–C920–A5BA). Keepa copy of the record at each site.

Table 8 Configuration form

Array name:

Array WWN:

Console LUN ID: (default = 0)

Disk group information

(default = default disk group)Disk group name:

Device count:

(none, single, or double)Spare policy:

(online or near-online)Disk type:

(default = 95%)Occupancy alarm:

Host information

126 Managing remote replication

Table 8 Configuration form (continued)

(default = \Hosts\)Folder name:

Host name:

Operating system:

WWN:For each HBA port:

Virtual disk information

(default = \Virtual Disks\)Folder name:

Virtual disk name:

Disk group:

Size:

(Vraid0, Vraid1, Vraid5)Redundancy level:

(Mirrored write-back, unmirrored write-back)Write cache policy:

(On, off)Read cache policy:

(Read/write, read-only)Read/write permissions:

(default = 0)OS unit ID:

(None, Path A FO, Path A FO/FB, Path B FO, Path B FO/FB)Preferred controller

Host name:Presentation:

LUN:

DR group information

Array name:Source:

Virtual disk members:

Array name:Destination:

Virtual disk members:

Failsafe mode: (disabled, enabled)Parameters:

Write mode: (synchronous, enhanced asynchronous, orbasic asynchronous)

Destination mode: (none, read-only)

Upgrading controller softwareThe following documents provide detailed information on upgrading controller software. Makesure you have these documents available before performing the upgrade.

• Updating Product Software Guide for your array model and controller software version. Youcan access this document from the Manuals page of the HP Business Support Center website:http://www.hp.com/support/manuals.In the Storage section, click Disk Storage Systems and then select your product from EVA DiskArrays.


Upgrading controller software 127


10 Support and other resourcesContacting HP

HP technical supportTelephone numbers for worldwide technical support are listed on the HP support website:http://www.hp.com/support/Collect the following information before calling:

• Technical support registration number (if applicable)

• Product serial numbers

• Product model names and numbers

• Error messages

• Operating system type and revision level

• Detailed questionsFor continuous quality improvement, calls be recorded or monitored.

Subscription serviceHP recommends that you register your product at the Subscriber's Choice for Business website:http://www.hp.com/go/wwalertsAfter registering, you will receive email notification of product enhancements, new driver versions,firmware updates, and other product resources.

Documentation feedbackHP welcomes your feedback.To make comments and suggestions about product documentation, please send a message [email protected] submissions become the property of HP.

Product feedbackTo make comments and suggestions about HP P6000 Continuous Access, please send a messageto [email protected].

Related information

DocumentationThe following documents are referenced in this guide:

• HP P6000 Replication Solutions Manager Release Notes


• HP P6000 EVA Command View User GuideYou can find these documents on the Manuals page of the HP Business Support Center website:http://www.hp.com/support/manualsIn the Storage section, click Storage Software, and then select your product.The HP Enterprise Virtual Array Configuration Best Practices White Paper is located on the StorageArray Systems white papers website:

128 Support and other resources

http://www.hp.com/support/

http://www.hp.com/go/wwalerts

mailto:[email protected]

mailto:[email protected]


http://h18006.www1.hp.com/storage/arraywhitepapers.htmlThe following SAN-related documents are located on the HP Storage Networking website:http://h18006.www1.hp.com/storage/networking/index.html


• HP Essentials Data Replication Designer 1.0 User GuideThe following may be useful when planning your array configuration:

• HP 4400 Enterprise Virtual Array (EVA4400) Performance White Paper:http://h71028.www7.hp.com/ERC/downloads/4AA1-8473ENW.pdf

• Storage Solutions from HP website athttp://h71028.www7.hp.com/enterprise/cache/322207-0-0-0-121.html

HP websitesFor additional information, see the following HP websites:

• HP:http://www.hp.com

• HP Storage:http://www.hp.com/go/storage

• HP Partner Locatorhttp://www.hp.com/service_locator

• HP Software Downloads:http://www.hp.com/support/manuals

• HP Software Depot:http://www.softwarehp.com

• HP Single Point of Connectivity Knowledge (SPOCK):http://www.hp.com/storage/spock

• HP SAN manualshttp://www.hp.com/go/sdgmanuals

Typographical conventionsTable 9 Document conventions

ElementConvention

Cross reference links and email addressesBlue text: Table 9 (page 129)

Website addressesBlue, underlined text: http://www.hp.com

Bold text • Keys that are pressed

• Text entered into a GUI element, such as a box

• GUI elements that are clicked or selected, such as menu andlist items, buttons, tabs, and check boxes

Text emphasisItalic text

Typographical conventions 129

http://h18006.www1.hp.com/storage/arraywhitepapers.html

http://h18006.www1.hp.com/storage/networking/index.html

http://h71028.www7.hp.com/ERC/downloads/4AA1-8473ENW.pdf

http://h71028.www7.hp.com/enterprise/cache/322207-0-0-0-121.html

http://www.hp.com

http://www.hp.com/go/storage

http://www.hp.com/service_locator


http://www.softwarehp.com


http://www.hp.com/go/sdgmanuals

http://www.hp.com

Table 9 Document conventions (continued)

ElementConvention

Monospace text • File and directory names

• System output

• Code

• Commands, their arguments, and argument values

Emphasized monospace textMonospace, bold text

An alert that calls attention to important information that if notunderstood or followed can result in personal injury.WARNING!

An alert that calls attention to important information that if notunderstood or followed can result in data loss data corruption,or damage to hardware or software.

CAUTION:

An alert that calls attention to essential information.IMPORTANT:

An alert that contains additional or supplementary information.NOTE:

130 Support and other resources

GlossaryA

ABM array-based managementarray Synonymous with storage array, storage system, and virtal array. A group of disks in one or

more disk enclosures connected to two controllers running controller software that presents diskstorage capacity as one or more virtual disks. See also virtual array, storage system.

array-basedmanagement

A management structure in which HP P6000 Command View is installed on the managementmodule within the EVA controller enclosure.

asynchronous A term used to describe computing models that eliminate timing dependencies between sequentialprocesses. In asynchronous replication, the array controller acknowledges that data has beenwritten at the source before the data is copied at the destination. Asynchronous write mode is anoptional DR group property. See also synchronous.

B

bandwidth The transmission capacity of a link or system, usually measured in bits per second (b/s).bandwidth latencyproduct

The measurement of the ability to buffer data; the raw transfer speed in bytes/second times theround-trip latency in seconds.

bidirectional An array that contains both source and destination virtual disks. A bidirectional configurationallows multidirectional I/O flow among several arrays.

C

controller software Controller software manages all aspects of array operations, including communication with HPP6000 Command View. VCS is the controller software for the EVA3000/5000 models. XCS isthe controller software for all other EVA array models.

EVA ContinuousAccess

A storage-based HP solution consisting of two or more arrays performing disk-to-disk replication,along with management user interfaces that facilitate configuring, monitoring, and maintainingthe replicating capabilities of the arrays.

D

data currency A measure of how current the last I/O on the DR group destination member is when comparedto the last I/O written to the DR group source member. The time difference between the last I/Owritten to the source member and the last I/O written to the destination member represents theamount of data that would be lost if the source member was no longer available, (assuming anon-recoverable event at the source site). See also RPO.

DC-Management Dynamic capacity management feature that enables you to extend (increase) or shrink (decrease)the size of a host volume without disrupting host I/O.

default disk group The disk group created when the array is initialized. The disk group must contain a minimum ofeight disks. The maximum is the number of installed disks.

destination The targeted recipient (for example, array or virtual disk) of replicated data. See also source.disaster tolerance The capability for rapid recovery of user data from a remote location when a significant event

or disaster occurs at the local computing site. It is a special combination of high-availabilitytechnology and services that can continue the operation of critical applications in the event of asite disaster. Disaster-tolerant systems are designed to allow applications to continue operatingduring the disaster recovery period.The capability for rapid recovery of user data from a remotelocation when a significant event or disaster occurs at the local computing site. It is a specialcombination of high-availability technology and services that can continue the operation of criticalapplications in the event of a site disaster. Disaster-tolerant systems are designed to allowapplications to continue operating during the disaster recovery period.

disk group A named group of disks selected from all available disks in an array. One or more virtual diskscan be created from a disk group.

131

DR group Data Replication group. A logical group of virtual disks in a remote replication relationship witha corresponding group on another array.

DR group memberstates

Normal. Remote replication involving the virtual disk is normal. There is no logging or merginginvolving the virtual disk.Full Copy. The DR group log threshold has been reached and the virtual disk is involved in a fullcopy.Async Merging (Adding). The virtual disk is a member of an enhanced asynchronous DR group,and is performing a full copy. This can happen when a virtual disk is added to a DR group orthe DR group log is full.Async Merging (Removing). The virtual disk is a member of an enhanced asynchronous DR group,and is being removed from a source DR group. Removal completes when all transactions in theDR group log have merged to the destination DR group virtual disk.Async Merging (Shrinking). The virtual disk capacity is being reduced. This can occur forsynchronous, basic asynchronous, or enhanced asynchronous DR groups.Unknown. The virtual disk copy state cannot be determined.

DR relationship When one EVA mirrors data to a second, remote EVA, they are said to have a DR relationship.dual fabrics Two independent fabrics providing multipath connections between Fibre Channel end devices.

E

enabled host A host that is equipped with a replication manager host agent.enhancedasynchronous

A write mode in which all host write I/Os are added to write history log. The controller thenacknowledges that data has been written at the source before the data is copied at the destination.

event Any significant change in the state of the Enterprise storage system hardware or softwarecomponent reported by the controller to HP P6000 Command View.

F

fabric A network of Fibre Channel switches or hubs and other devices.failover An operation that reverses replication direction so that the destination becomes the source and

the source becomes the destination. Failovers can be planned or unplanned and can occurbetween DR groups, managed sets, fabrics or paths, and array controllers.

failsafe A safe state that devices automatically enter after a malfunction. Failsafe DR groups stop acceptinghost input and stop logging write history if a group member becomes unavailable.

fast copy The process for quickly synchronizing the data on a source virtual disk and a destination virtualdisk by coping only data blocks that have changed. As I/O is written to the write history log, abitmap tracks the region of the virtual disk written. Only the regions that are indicated by thecorresponding bit in the bitmap are copied to the destination virtual disk. This process synchronizesthe source and destination virtual disks faster than a full copy.

full copy The process of copying all data written on a source virtual disk directly to the destination virtualdisk. If a data block contains all zeros, a zeroing message is sent to the destination array's virtualdisk for the corresponding data block. This minimizes the amount of data that must be written tothe destination virtual disk. When the full copy is complete, the source and destination virtualdisks contain the same data (synchronized).

G

GBIC Gigabit Interface ConverterGBps Gigabytes per second. A measurement of the rate at which the transfer of bytes of data occurs.

A GBps is a transfer rate of 1,000,000,000 (109) bytes per second.Gbps Gigabits per second. A measurement of the rate at which the transfer of bits of data occurs.

Nominally, a Gb is a transfer rate of 1,000,000,000 (109) bits per second.

132 Glossary

general-purposeserver

A server that runs customer applications such as file and print services. HP P6000 CommandView and HP P6000 Replication Solutions Manager can be used on a general purpose serverin limited configurations.

H

home The DR group that is the preferred source in a replication relationship. By default, home is theoriginal source, but it can be set to the destination DR group.

host A computer that runs user applications and uses the information stored on an array.host volume Storage capacity that is defined and mountable by a host operating system.

I

initialization A configuration step that binds the controllers together and establishes preliminary data structureson the array. Initialization also sets up the first disk group, called the default disk group, andmakes the array ready for use.

intersite link A connection from an E-Port on a local switch to an E-Port on a remote switch.ISL Intersite link.IVR Inter-VSAN Routing

M

managed set Selected resources grouped together for convenient management. For example, you can createa managed set to manage all DR groups whose sources reside in the same rack.

managementserver

A server on which HP Enterprise Virtual Array (EVA) management software is installed, such asHP P6000 Command View and HP P6000 Replication Solutions Manager.

merge The act of transferring the contents of the write history log contents to the destination virtual diskto synchronize the source and destination.

mirrorclone Mirrorclone replication establishes and maintains a copy of an original virtual disk via a localreplication link.When first created (and whenever resynchronized by an action or command), amirrorclone is said to be synchronized. In a synchronized state, the mirrorclone is automaticallyupdated whenever the source virtual disk is updated. When local replication between asynchronized mirrorclone and the source is stopped by an action or command, the mirrorcloneis said to be fractured. In a fractured state, the mirrorclone is not updated when the source virtualdisk is updated. At the instant replication is stopped, the mirrorclone is a point-in-time copy of itssource.

N

nearline storage On-site storage of data on media that takes only slightly longer to access than online storagekept on high-speed disk drives.

normalization The background process of copying the contents of a source virtual disk to a snapclone. Thesnapclone is dependent on the source until normalization is complete. Also called unsharing.

O

online storage An allotment of storage space that is available for immediate use, such as a peripheral devicethat is turned on and connected to a server.

P

presentation The array controller's act of making a virtual disk accessible to a host computer.

R

remote copy A copy of a virtual disk on the destination array.RPO Recovery Point Objective. The maximum age of the data you want the ability to restore in the

event of a disaster. For example, if your RPO is 6 hours, you want to be able to restore systems

133

back to the state they were in as of no longer than 6 hours ago. To achieve this objective, youneed to be making backups or other data copies at least every 6 hours.

RTO Recovery Time Objective. The time needed to recover from a disaster—usually determined byhow long you can afford to be without your systems.

RWP Replication Workload Profiler

S

SAN Storage area network. A network of storage devices and the initiators that store and retrieveinformation on those devices, including the communication infrastructure.

server-basedmanagement

Management from a server. See also management server.

SFP Small Form Factor Pluggable transceiver.snapclone A copy that begins as a fully allocated snapshot and becomes an independent virtual disk. Applies

only to the HP EVA.snapshot A nearly instantaneous copy of the contents of a virtual disk created without interrupting operations

on the source virtual disk. Snapshots are typically used for short-term tasks, such as backups.source The virtual disk, DR group, or virtual array where I/O is stored before replication. See also

destination.SPOF Single point of failure.standbymanagementserver

A backup management server. See management server.

storage system A system consisting of one or more arrays; synonymous with virtual array. See also array.synchronous A term used to describe computing models that perform tasks in chronological order without

interruption. In synchronous replication, the source waits for data to be copied at the destinationbefore acknowledging that it has been written at the source. See also asynchronous.

V

virtual array Synonymous with disk array and storage system; a group of disks in one or more disk enclosurescombined with control software that presents disk storage capacity as one or more virtual disks.See also virtual disk.

Virtual ControllerSoftware (VCS)

See controller software.

virtual disk Variable disk capacity that is defined and managed by the array controller and presented tohosts as a disk. May be called Vdisk in the user interface.

Vraid The level to which user data is protected. Redundancy is directly proportional to cost in terms ofstorage usage; the greater the level of data protection, the more storage space is required. Seealso: Vraid0, Vraid1, Vraid5, Vraid6.

Vraid0 Optimized for I/O speed and efficient use of physical disk space, but provides no dataredundancy.

Vraid1 Optimized for data redundancy and I/O speed, but uses the most physical disk space.Vraid5 Provides a balance of data redundancy, I/O speed, and efficient use of physical disk space.Vraid6 Offers the features of Vraid5 while providing more protection for an additional drive failure, but

uses additional physical disk space.

W

WDM Wavelength Division Multiplexing. The ability to have multiple optical signals share a singleoptical cable.

write history log A dedicated area of disk capacity used to record host write I/O to the source virtual disks.

134 Glossary

X

XCS See controller software.

135

Index

AAIX

procedure to resume I/O, 119application

and bandwidth, 20and disk groups, 35and DR groups, 24determining peak load, 18failover, 26recovery, 15

asynchronous modedescription, 21

asynchronous write modedescription, 8specifying, 99

BB-series switch configuration, 52backup

configuration, 100manual, 126procedure, 126using HP P6000 Replication Solutions Manager, 126using HP Storage System Scripting Utility, 126

bandwidthand performance, 18and RPO, 18evaluating, 20in bidirectional replication, 46reducing cost, 17

bandwidth capacity, 18best practices

before making a normalization, 124support procedures, 124throttling merge I/O, 124

bidirectional replication, 46boot from SAN, 50bootless DR group failover (Linux), 122

CC-series switch configuration, 52cabling arrays

verifying, 54cascaded replication, 49concepts

remote replication, 8configuration

backing up, 100, 126backing up manually, 126backing up with HP Storage System Scripting Utility,

126basic, 23bidirectional replication, 46cascaded replication, 49fan-in replication, 48

five-fabric, 29for application failover, 26limits, 23low availability, 27rules, 24, 25single HBA, 29single-fabric, 27single-switch, 28six-fabric, 32system fan-out replication, 47with HP Cluster Extension , 26with HP Continentalcluster, 27with HP Metrocluster Continuous Access, 27with ServiceGuard, 27

controller softwareconfiguration rules, 24upgrading, 127

costand distance, 17

creatingdestination snapclone before normalization, 124DR groups, 98virtual disks, 96

Ddata replication, 8Data Replication Designer

and latency, 17, 20data replication group see DR groupdata replication protocol, 38DC-Management, 58default disk group, 96destination loss

recovery, 115destination virtual disk, 8disaster planning, 103disaster tolerance

definition, 15threat radius, 15

disk groupcreating, 96failure, 113failure on destination array, 115failure on source array, 114occupancy alarm, setting, 35protection level, 35

disk groupsfor bidirectional replication, 46planning, 35write history log, 42

disk protection levelselecting, 35

distanceand cost, 17and link technologies, 17

document

136 Index

conventions, 129related documentation, 128

documentationHP website, 128providing feedback, 128

DR groupbidirectional, 46bootless failover (Linux), 122cascaded, 49creating, 98description, 8, 36fan-in, 48guidelines, 36log disks, 9, 42log size, 43planning, 36rules, 24system fan-out, 47virtual disk member, 98

DR group write history logplanning for, 42specifying location, 44specifying size, 43

Eenhanced asynchronous mode

description, 21examples

one-way latencies, 16

Ffailback

procedure, 110to new storage hardware, 110to original source, 110

failed disk group, 113failover

AIX, 119application, 26bootless, 50choosing a procedure, 104controller, 10defined, 10fabric or path, 10HP-UX, 118interfaces, 104Linux, 119NetWare, 120OpenVMS, 118planned, 103, 105site, 103Solaris, 120testing, 100Tru64, 118unplanned, 103, 108versus component repair, 103VMware, 121Windows, 121

failsafe mode, 10

recovering from failsafe-locked, 108failsafe on link-down/power-up, 11fan-in replication, 48FATA drives, considerations, 38FC-to-IP

and distance, 17configuration, 25in five-fabric configuration, 29

feedbackdocumentation, 128product, 128

Fibre Channel switch configurationB-series, 52C-series, 52H-series, 54M-series, 54verifying, 51

five-fabric configuration, 29five-zone configurations, 66full copy, 43, 124

automatic, 110

HH-series switch configuration, 54hardware failure, 115HBA

configuration, 29configuration rules, 24

helpobtaining, 128

high availabilitydefinition, 15

Homefailing back to, 110

hostmultipath software, 96specifying HBAs, 98

HPsupport website, 128technical support, 128

HP Cluster Extension, 15configuration, 26

HP Command View EVAPerf, 14HP Continentalcluster, 15

configuration, 27HP Essentials Data Replication Designer, 14HP Metrocluster, 15HP Metrocluster Continuous Access

configuration, 27HP OpenVMS

procedure to detect devices, 118HP P6000 Business Copy

license, 124HP P6000 Command View

password, 51HP P6000 Continuous Access

basic configuration, 23definition, 7implementing, 51

137

license, 58HP P6000 Replication Solutions Manager

backing up the configuration, 126installing, 58

HP SCSI-FCP data replication protocol, 38HP-FC data replication protocol, 38HP-UX

application recovery, 15procedure to detect devices, 118

II/O consistency, 22implementing

remote replication, 51implicit LUN transition, 37initializing arrays, 96installing

HP P6000 Replication Solutions Manager, 58license, 58

interface optionsfor failover, 104

intersite linkchoosing, 17definition, 7

Llatency

and performance, 16definition, 16determining, 17evaluating, 17for sample distances, 16in point-to-point networks, 17in routed networks, 17

licenseinstructions, 58

LifeKeeperbootless failover , 122

LifeKeeper clustersRed Hat and SUSE Linux, 122

link technologiesand peak load, 18FC-to-IP, 25long-distance GBICs, 24supported distances, 17WDM, 24

Linuxapplication recovery, 15procedure to resume I/O, 119

load balancing, 125log disks, 9

description, 9, 42full copy, 43, 124normalization, 43

log size, 43logging, 114, 124

enhanced asynchronous mode, 42synchronous or basic asynchronous mode, 42

long-distance GBIC

configuration, 24supported distance, 17

MM-series switch configuration, 54managed sets, 9management server

configuration rules, 24setup, 100zoning, 70

merging, 124and I/O performance, 124throttling merge I/O, 110

Microsoft Windowsapplication recovery, 15

modesfailsafe, 10write, 99

multipathconfiguration rules, 24in single-HBA configuration, 29in single-switch configuration, 28

multipath softwarerequirement, 96

Nnear-online disk

and DR group write history log, 44NetWare

procedure to resume I/O, 120normalization, 43, 124

Ooccupancy alarm

setting, 35operating system

considerations, 50

Ppassword

HP P6000 Command View, 51path failover, 10peak load

measuring, 18performance

and bandwidth, 18and latency, 16

planned failoverdefined, 103procedure, 105

planning for disaster, 103preferred controller

specifying, 97presentation blocking

disabling, 11presenting virtual disks, 98, 100product

providing feedback, 128proxy reads, 37

138 Index

Rrecovery

after destination loss, 108choosing a procedure, 104from destination disk group failure, 115from disk group failover, 113

Red Hat LinuxLifeKeeper clusters, 122

related documentation, 128remote copy, 8remote replication

concept, 8implementing, 51in a mixed array environment, 124

remote sitechoosing the location, 14

replicationbidirectional, 46cascaded, 49fan-in, 48system fan-out, 47

Replication Solutions Manager interfacemanaged sets, 9

Replication Workload Profiler (RWP), 14resume command, 125RPO

and bandwidth, 18and write mode, 20definition, 18

RTOand write mode, 20definition, 15

SSAN

booting from, 50SAN data tools, 14

HP Command View EVAPerf, 14HP Essentials Data Replication Designer, 14Replication Workload Profiler (RWP), 14

SAS Midline drives, considerations, 38Secure Path

dynamic load balancing, 96Linux bootless failover, 122resuming I/O on Solaris, 120specifying preferred controller, 97

ServiceGuardsupported configuration, 27

setting upmanagement servers, 100

SFPconfiguration, 24

single-fabric configuration, 27single-HBA configuration, 29single-switch configuration, 28six-fabric configuration, 32six-zone configurations, 67snapclone

creating before normalization, 124

Solarisprocedure to resume I/O, 120

source virtual disk, 8SPOF

and high availability, 15basic configuration, 23HBA configuration, 24

stale data, 114Storage System Scripting Utility (SSSU), 112, 126Subscriber's Choice, HP, 128support procedures, 124SUSE Linux

LifeKeeper clusters, 122suspend command, 125synchronous mode

description, 22synchronous write mode

description, 8specifying, 99

system fan-out replication, 47

Ttechnical support

HP, 128service locator website, 129

threat radiusdefinition, 15determining, 16

throttling, 110merge I/O after logging, 124

Tru64 UNIXprocedure to detect devices, 118

tunnel thrash, 41two-fabric configurations, 59

Uunplanned failover, 103

procedure, 108upgrading controller software, 127

Vverifying array setup, 51virtual disks

and bidirectional replication, 46creating, 96preferred controller, 97presenting, 98, 100

VMwareprocedure to resume I/O, 121

WWDM

and distance, 17configuration, 24

websitesHP, 129HP documentation, 128HP Metrocluster, 27HP Subscriber's Choice for Business, 128

139

HP support, 128Windows

procedure to resume I/O, 121write history log, 9

planning for, 42specifying location, 44specifying size, 43

write modeasynchronous, 21choosing, 20enhanced asynchronous, 21selecting, 99synchronous, 22

write modesasynchronous, 8defined, 8synchronous, 8

write order, maintaining correct, 22

Zzones

creating, 58zoning, 24

in single-switch configuration, 28single-fabric configuration, 27

140 Index

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