VERITAS FileServer Edition™

Managing Consolidated FileServers for Performance andAvailability

Table of Contents

Introduction ..................................................................................................................................................................1

The VERITAS File Server Edition ..................................................................................................................................2

Consolidating File Servers ............................................................................................................................................3

File Server Performance with VERITAS File Server Edition ..........................................................................................4

Inherent performance benefits of the platform .......................................................................................................4

Configurable performance improvements................................................................................................................4

The QuickLog Performance Accelerator..................................................................................................................4

Striping ...................................................................................................................................................................5

Improving File Server Availability .................................................................................................................................6

Online storage administration.................................................................................................................................6

Implementing Redundant Storage Techniques .........................................................................................................7

Implementing Failover with the HA Version ............................................................................................................7

Simplified Administration .............................................................................................................................................9

Storage Administration Interface ............................................................................................................................9

Consolidating Windows and UNIX File Server Administration ...............................................................................10

Summary ....................................................................................................................................................................12

Introduction

Today’s computer users expect instant access to data – anytime and anywhere. For storage administrators, theseexpectations can pose significant challenges. Critical data resides not only in high performance database systems, butalso in unstructured files on desktops and, increasingly, on shared file systems hosted by file servers.

Administrators responsible for maintaining these file servers, whether for internal use or for external customers orpartners, must do so in an environment characterized by:

◆ Growing storage demands

◆ Heterogeneous clients

◆ Numerous, fragmented servers serving different sets of clients

◆ High availability requirements (often 24x7)

A common scenario is that a company gradually adds file servers over time, with administrators eventually supportingmultiple file servers running on different platforms and operating systems, such as Windows and UNIX. This can createan ongoing administrative headache, particularly when faced with continually growing amounts of data and lowtolerance for administrative downtime. In this environment, file server administration is frequently an exercise in adhoc troubleshooting and buying more hardware. Special-purpose file server hardware may improve performance, butat the cost of implementing rigid, proprietary systems that increase overall system complexity.

This situation doesn’t have to be so grim. We do in fact have the tools and products to improve file server performanceand data availability on existing, commodity hardware, and to simplify the tasks of managing these systemsproactively. VERITAS Software has integrated and packaged these solutions into a software solution optimized forhosting file system data in file servers or messaging environments.

The VERITAS File Server Edition is a tightly integrated software suite that improves the manageability, performanceand availability of file servers using Sun SPARC systems. The File Server Edition supports both NFS and CIFS filesharing, so you can consolidate file servers supporting mixed Windows and UNIX environments. And it is built onVERITAS Software’s industry-leading storage management solutions.

This paper describes the components of the File Server Edition product, then discusses how system administratorscan use the product to improve the performance, availability and manageability of their file servers.

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The VERITAS File Server Edition

The VERITAS File Server Edition provides a packaged, integrated solution for improving file server performance,availability and manageability for both UNIX and Windows clients. The product components include industry-leadingstorage management solutions, integrated and optimized for the file server environment:

◆ The VERITAS File System™ is a journaling file system that provides better performance and availability thanthe standard UNIX File System (UFS).

◆ The VERITAS Volume Manager™ is a logical volume management solution that greatly simplifies volumemanagement and supports software-based RAID, including mirroring and striping for optimal performanceand reliability.

◆ VERITAS QuickLog™ is a specialized write accelerator for write-intensive environments.

◆ Samba is an open source solution for UNIX servers that enables Windows and UNIX clients to share files andresources across a network.

An optional HA (High Availability) version of the File Server Edition integrates the following components as well:

◆ VERITAS Cluster Server (VCS), a highly flexible and scalable application monitoring and failover solution.

◆ VCS agents for NFS, CIFS, and VERITAS QuickLog.

The VERITAS File Server Edition integrates all of these products into a packaged solution optimized for file servers. Asingle graphical interface supports file system and volume management operations, and VERITAS Software supports

the entire, integrated solution – even the open source Samba component.

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Consolidating File Servers

Environments with multiple file servers can realize many benefits by consolidating them into a single server. Theseinclude:

◆ Reduced management overhead. One administrator can manage the consolidated environment; there is oneset of backups, etc.

◆ Consolidated hardware investment (making more efficient use of powerful servers and storage)

◆ Reduced network traffic

In a consolidated environment, reliability and availability are more critical than before, as outages affect greaternumbers of clients. The VERITAS File Server Edition makes server consolidation a viable solution because it providesan inherently more reliable and available platform than native UNIX platforms, and because it gives the systemadministrator additional tools to ensure the availability of data on the consolidated server. The High Availabilityversion of the File Server Edition includes automated application monitoring and failover for environments withcritical availability requirements.

In environments with both UNIX and Windows clients, file server consolidation can provide better communication andfile sharing between UNIX and Windows clients and simplify administrative tasks. The VERITAS File Server Editionenables mixed UNIX and Windows-based file server consolidation using Samba, open source software for UNIX. Sambaimplements the Common Internet File System (CIFS), the remote access protocol published by Microsoft.

Samba lets a UNIX system operate as a CIFS file server for Windows systems. The support is completely transparentto the Windows clients because Samba “speaks the same language” as the Windows systems. There is no clientsoftware to install on Windows clients. The Samba server appears in the Windows Network Neighborhood for theWindows clients and the files can be mapped to drive designations as if they resided on a Windows file server. Sambaalso enables print sharing, name resolution, and authentication services.

As part of the VERITAS File Server Edition, Samba is an ideal solution for integrating file servers in mixed Windowsand UNIX environments. Samba has all of the strengths of an open source solution, including the collaboration, testingand enhancements of the worldwide developer community. VERITAS Software participates in Samba development bysubmitting enhancements back to the Samba community.

The File Server Edition integrates all of the benefits of the open source Samba solution with VERITAS’ industry-leadingstorage management software and support. The Samba CIFS Server runs on the VERITAS File System, which providessignificant performance and manageability improvements over running on UFS. The VERITAS File System and VolumeManager products improve overall system availability and reliability, and the HA version of the File Server Edition providesapplication-specific failover for the file server programs, reducing the risk of downtime in a consolidated environment.

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Consolidated UNIX/Windows environment using one SPARC Solaris server with VERITAS File Server Edition.

File Server Performance with VERITAS File Server Edition

Whether you run NFS alone or the mixed NFS/CIFS environment enabled by Samba, running these processes with theVERITAS File Server Edition provides significant performance benefits over running on UFS.

Inherent performance benefits of the platform

The VERITAS File Server Edition uses the VERITAS File System (VxFS), a high performance, fast-recovery file systemoptimized for business-critical file server applications and data intensive workloads.

UFS allocates space in fixed blocks. VxFS uses extent-based allocation, which provides better performance for mostapplications. An extent is one or more adjacent blocks of data in the file system.

Files written in larger extents have less fragmentation and fewer indirect pointers than files written in the smaller,fixed block sizes of traditional UNIX file systems. Disk I/O can occur in units of multiple blocks, so applications spendless time waiting for the disk head to cycle to the next set of blocks. For sequential I/O, multiple-block operations areconsiderably faster than block-at-a-time operations.

More information on the performance can be found in the VERITAS File System Performance white paper in theReference Library at the VERITAS web site, www.veritas.com.

Configurable performance improvements

Other benefits can be achieved easily with minimal tuning and configuration on the part of the system administrator.

For example, the VERITAS Storage Administrator, the graphical interface for the File Server Edition, provides asimple, graphical interface for identifying and removing I/O bottlenecks. The system administrator can also configurethe QuickLog performance accelerator and implement striping techniques to further improve performance. These aredescribed below.

The QuickLog Performance Accelerator

The QuickLog accelerator provides ongoing performance improvements for any write-intensive environment(such as CIFS, NFS, or messaging servers) using the VERITAS File System. It does so by enabling parallelupdates to file data and the intent log maintained by the file system.

The VERITAS File System is a journaling file system – it maintains a journal, or intent log, which speedsrecovery after any outage. File servers and messaging servers typically have numerous small files withfrequent creation and updates. This generates more logging activity to track the metadata (such as inodeinformation) in the journal.

With QuickLog, the file system journals can be kept on a separate, dedicated journal volume. This enablesjournal updates to occur in parallel with access to the file data, mitigating any performance impact ofmaintaining the journal. Together with extent-based allocation and striping capabilities, the File ServerEdition provides NFS performance improvements of 110% over the standard UFS. VERITAS has also trackedperformance improvements of more than 10 times UFS in messaging environments, such as e-mail and newsservers. (For more information, see the VERITAS File Server Edition Performance Briefs, available on theVERITAS web site.)

Multiple VxFS file systems can share the dedicated journal volume; QuickLog interleaves journal updatesfrom multiple file systems to utilize the volume space most efficiently.

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Like all of the Edition components, QuickLog is completely transparent to the applications and users thataccess it. In addition, it is tightly integrated into the overall solution – using QuickLog requires only a one-time setup, and VERITAS Cluster Server agents offer automated failure detection and failover for QuickLog.

A more detailed description of the QuickLog accelerator can be found in the File Server Edition: VERITASQuickLog white paper, available from the VERITAS web site.

Striping

Disk striping speeds file access by interleaving a volume’s data across two or more physical disks, reducingtime spent waiting for disk head movements. With the VERITAS Volume Manager, you can create stripedvolumes (RAID 0), striping with mirroring (RAID 0+1), mirroring with striping (RAID 1+0) or striping withparity (RAID 5) – all at the software level, using commodity disk devices.

Simple striping (RAID 0) improves performance by interleaving data across multiple physical devices. Thisspeeds performance, but has implications for availability. The failure of any device in the striped set leads tothe failure of the entire striped logical volume. For this reason, striping is usually combined with eithermirroring or parity checking, to provide redundancy and protection against device failure.

Volume Manager supports two combinations of mirroring and striping (RAID 0+1 and RAID 1+0), as well asstriping with distributed parity (RAID 5). These combine the improved performance of striping with the dataredundancy of mirroring.

◆ RAID 1+0 is mirroring plus striping – the volume is first mirrored, then each mirror is striped. Thisprovides the speed of striping on writing each mirrored set. However, if there is a failure of a subdisk, theentire mirror must be taken offline and resynched to correct the problem.

◆ RAID 0+1 is striping plus mirroring – the volume is first striped, then each column of the striped set ismirrored. If the stripe is large enough to have multiple subdisks, each subdisk can be mirrored individually.This reduces recovery time in case of an error, as only the smaller stripe must be restored to recover froma physical failure.

◆ RAID 5 combines the enhanced performance of striping with the increased availability provided by paritychecking. Using the RAID 5 specification for striping with parity, the parity information is distributedamong the volumes in the striped set. RAID 5 is useful for providing high availability with limited diskresources. RAID 5 logs provide fast volume resynchronization after a disk crash.

Whichever striping layout you choose, software-based striping is highly flexible compared with hardware-based RAID devices. For example, the devices in a striped set do not have to be of the same size and speed,and can contribute different amounts of storage to the logical volume. And it is easy to add devices to astriped set or otherwise resize storage allocations. With this flexibility, you can optimize the performance ofexisting storage hardware according to system usage and requirements.

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Improving File Server Availability

The File Server Edition provides an inherently more reliable and available platform for file servers than native UNIXenvironments alone, as it is less susceptible to file system panics and restarts much faster after a failure.

◆ Reduced file system panics

Disks, being physical devices, degrade over time. The larger the file system, the more frequently the systemencounters bad sectors or other I/O problems caused by the physical disk device. The UNIX file system has atendency to generate file system panics when it discovers problems, even failures in noncritical subsystems.

The VERITAS File System protects the UNIX environment from unnecessary file system panics. If it detects aproblem, it isolates the problem without causing failures on the file system as a whole. This eliminates arelatively common source of UNIX file system outages.

◆ Journaling for fast file system recovery

As a journaling file system, the VERITAS File System provides much faster restart after a failure or outagethan UFS. Writes or updates to the file system are tracked in an intent log or journal until they are written tothe disk. If a failure does occur, the VERITAS File System uses the journal to restore itself quickly to aconsistent state. It replays the log record and completes any incomplete writes. This process takes only a fewseconds, regardless of the size of the file system, and ensures data integrity.

In contrast, UFS buffers file system writes to a cache. It then synchronizes those writes to disk. After asystem outage, UFS performs a file system check (fsck), which walks through the file system metadata,examining and repairing structures as necessary. This requires a full scan of the file system. As file systemsgrow in size, the time to restart takes longer and longer.

Because system administrators can perform storage administration tasks while systems are online and available, theFile Server Edition reduces the planned, administrative downtime necessary to maintain production systems. Inaddition, system administrators can configure redundant storage configurations to further improve availability. Siteswith critical availability needs can implement the High Availability version of the File Server Edition to provideautomated application monitoring and failover capabilities. These features are described below.

Online storage administration

One of the key strengths of the File Server Edition is that system administrators can perform routine maintenancewhile the system is up and available. These administrative tasks include:

◆ Adding disks

◆ Replacing faulty or slow disk devices

◆ Resizing storage allocations

◆ Defragmenting storage

◆ Reconfiguring disk devices (for I/O load balancing or new application support)

◆ Reconfiguring mirrored or striped volumes

With native file system utilities, all of these basic operations require taking data offline. The VERITAS File ServerEdition performs all of these operations online, safely. The users will be unaware of the maintenance operations.

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Implementing Redundant Storage Techniques

For critical data, the system administrator can implement software-based mirroring to ensure that a disk failure doesnot result in a loss of data. Administrators can implement this mirroring on a volume-by-volume basis, depending onthe nature of the data stored.

Software-based mirroring is highly flexible. Mirrored devices do not have to be of the same size or type. A mirroreddevice may be a logical volume composed of storage on multiple different devices.

If one of the mirrored devices fails, the hot relocation capabilities of the VERITAS Volume Manager automaticallycreate a second mirror on free space. This prevents the performance degradation that can otherwise occur when onemirrored device fails.

The VERITAS Volume Manager supports the identification of hot spare disks. In case of failures, the software firstattempts to use the hot spare disk to replace a failed disk. If hot spare disks are unavailable, any free space availableis used to maintain redundancy. The data can be swapped to the new disk while the system is running.

Implementing Failover with the HA Version

Disk mirroring protects against disk-level device errors. But the file server application itself is susceptible to otherkinds of errors, including application errors or OS errors.

The File Server Edition/HA includes the industry’s most flexible and scalable solution for high availability, VERITASCluster Server.

VERITAS Cluster Server monitors and manages application service groups – groups of application services that mustbe migrated together in the case of a failure. Application-specific agents monitor applications and automaticallyrestart or migrate them to another server if a failure occurs. Any node in a cluster may run multiple service groups,which may fail over to different servers according to the rules created by the administrator.

Unlike traditional, point-to-point availability solutions, VERITAS Cluster Server provides a highly flexible and scalablesolution. The product supports up to 32 nodes with cascading and multi-directional failover.

The VERITAS File Server Edition/HA includes Cluster Server agents for NFS and CIFS (Samba). In the case of a failure,the Cluster Server component migrates these services to another server. UNIX-connected NFS clients will see nofailure (but may experience a brief delay as the services migrate to the new server). Windows clients will probablyalso not experience any problems, as Windows NT automatically retries connections. However, some “nervous”applications may quickly retry and fail before the services can be restarted. In this case, the user will need toreconnect to the file server.

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❶ 4 service, 3 node cluster in normal operation.

❷ Node 2 fails. On failover, its load isbalanced across nodes 1 and 3.

❸ Node 1 fails, and all services failover to node 3.

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D D

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A A

C C

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D D

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A A

A A B

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The system administrator defines the failover policies, and can manage all multiple clusters and nodes from a single,Java-based management interface.

System administrators can use VERITAS Cluster Server to migrate services manually to alternate servers – this givessystem administrators a way to perform offline management tasks on a system while keeping vital data andapplications available. For sites with critical availability requirements, the File Server Edition/HA provides a high levelof availability with optimal flexibility and manageability.

For more information on the Cluster Server component of the File Server Edition/HA, see the VERITAS Cluster Serverwhite paper, available on the VERITAS web site.

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The Java™-based graphical interface provides a view of the services, systems, and resources being managed.

Simplified Administration

Simplified administration is one of the key objectives for file server consolidation. The VERITAS File Server Editionmakes the file server environment much easier to administer and maintain over time by consolidating administrativetasks within a single graphical interface and automating application monitoring and failover activities.

Storage Administration Interface

The VERITAS Storage Administrator is the integrated graphical interface for the File Server Edition. This interfaceallows one-step execution of common storage configuration tasks, most of which can occur while storage is online andavailable. It also provides a graphical presentation of storage bottlenecks and statistics.

With the File Server Edition/HA product, application-specific agents monitor critical processes so you don’t have to. Incase of a failure, the software automatically restarts or fails over to another server, according to the policies that youhave defined. Intelligent software makes the task of managing these servers much easier.

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The Storage Administrator graphical interface simplifies storage management tasks.

Consolidated Windows and UNIX File Server Administration

Most sites find that it is easier to manage one consolidated file server than multiple servers, particularly if you haveboth Windows and UNIX file servers. The Samba support integrated in the File Server Edition simplifies the jointadministration of Windows and UNIX clients significantly. Some of the key features are listed below.

◆ Authentication

Samba supports four levels of security: share, user, server, and domain. (It also supports guest access tospecific shares, so that users can connect without providing a password to generally available information.)

With share-level security, anyone who knows the password for a share can access it. Specific shares allowaccess to certain users – this is user-level security. Using server-level security, Samba validates users andpasswords through a separate SMB server before granting access to a share.

Using domain-level security, Samba becomes a member of an NT domain and uses the domain primarycontroller to authenticate users. Using this security scheme, the user does not have to supply a passwordeach time they access another Samba share in the NT domain.

◆ Encryption/passwords

When users log on to the file server, they must send their password. The File Server Edition supports bothencrypted and unencrypted password authentication. (Whether clients send encrypted passwords or notdepends on the client system. Windows 98 and Windows NT 4 with Service Pack 3 each require encryption.)Encrypted passwords are stored in a private directory on the file server. Only the root user should haveread/write access to this directory.

A password synchronization option in Samba helps keep the server’s version of the encrypted passwordsynchronized with the client version, for cases when the password changes.

◆ Access Control Lists (ACLs)

UNIX and Windows each use slightly different permission schemes. In each case, access to a file depends onthe user’s ID and the permission structure. Integrating UNIX files into the Windows NT domain securitysystem requires some translation on the part of the file server.

Windows NT identifies users with a Security ID (SID) – a combination of the user ID on the machine and amachine ID. To map to this scheme, Samba combines the UNIX user ID combined with a machine IDgenerated by Samba, thus creating an SID for the NT domain server.

Samba maps the standard UNIX user/group/world and read/write/executable permissions to thecorresponding NT permissions. UNIX world maps to the NT group everyone, the UNIX owner is the NT user,and the UNIX group is the NT local group.

◆ Setting up users’ disk shares

A shared service or resource is called a share in Samba. Disk shares point to directories on the file server.Administrators can create separate shares on the server according to system needs, with read-only sharesand writable shares. If users will have personal or “home” directories on the file server, then creating a[homes] disk share simplifies the process of managing and creating user directories.

The administrator creates UNIX accounts on the file server for the Windows users who will connect to theserver. If a user (for example, bfranklin) connects to the file server and requests the [bfranklin] share,Samba checks to see if one exists. If it does not, but if the user and password match in the local passworddatabase, then Samba automatically creates a [bfranklin] share in the [homes] share. Samba creates thesedirectories automatically, and only as they are requested.

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◆ Printer sharing

With Samba, Windows clients can access printers on the Samba server and its clients.

There are two ways to configure printer sharing. Administrators can add information about each printer toshare into a configuration file. Creating a generic [printers] share automatically configures printer shares foreach printer in the printer capabilities file.

On the Windows client, the available printers will now appear attached to the file server in the NetworkNeighborhood. Once the Windows client has the correct printer drivers, it can print to any of the sharableprinters.

◆ Naming

In Windows, the NetBIOS name server is called the Windows Internet Name Server (or WINS server). TheWINS server resolves names to IP addresses.

A File Server Edition server (using Samba) can be the primary WINS server for the Windows clients on anetwork.

◆ File Locks

To protect files from concurrent updates, Samba supports the traditional, file-level locking of the standardDOS and Windows/NT operating systems called Deny Mode. Supported deny mode locks are DENY_NONE,DENY_READ, DENY_WRITE, DENY_ALL, DENY_FCB, and DENY_DOS.

For example, if a client opens a file with DENY_WRITE, no other clients can open the file with write access(if the file wasn’t open previously). If a client opens a file with DENY_READ, no other client can open the filewith read permission. Opening a file with DENY_READ+DENY_WRITE prevents other clients from opening thefile with read or write permission. If a client opens a file with DENY_NONE, then any other client can openthe file with any permission.

◆ Oplocks (client file caching)

Samba supports Windows/NT client caching called oplock – opportunistic lock. When a client opens a file itcan ask for an exclusive oplock, which implied that this client is the only one who can access that file. Theserver will verify that there aren’t any clients who access the file and will grant the oplock if this is the case.This allows the client to cache the reads and manipulate the file locally (like locks), without accessing theserver. If later another client tries to open that file, the server sends an oplock break to the previous client(who opened the file with a exclusive oplock) and waits until the client acknowledges that the oplock isbroken.

Samba also supports level II oplocks (or shared oplocks), which allow multiple clients to access the same filefor reading. If the client asked for a an exclusive oplock during opening but the file is already opened forreading, the server will grant the client level II oplocks which implies that nobody writes to the file so theclient can cache the read data. Should any of the clients who have a level II oplock attempt to write to thefile, the server will issue an oplock break to all the clients who own level II oplock on that file. If a clientasked for an exclusive oplock and another client has the file for exclusive oplock, the server sends a messageto the exclusive oplock owner to downgrade its oplock to level II and will grant the requester a level IIoplock.

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Summary

The VERITAS File Server Edition combines intelligent storage management techniques (such as extent-basedallocation and logical volume management) with industry-leading solutions for remote file access and availability tocreate a flexible, configurable software solution for hosting critical file servers.

Using the File Server Edition, consolidating file servers is not only viable, it’s easy to do, because the software createsa better platform for hosting file servers. And with the integrated Samba support, it is no longer necessary ordesirable to maintain separate file servers for Windows and UNIX systems. Administrators can simplify the systemenvironment with a consolidated solution.

With the File Server Edition, administrators have the tools at hand to optimize the performance and availability ofcritical data – identifying storage bottlenecks, reconfiguring storage, and implementing mirroring and striping asnecessary for performance and availability requirements. And they can perform these tasks while data is online andavailable, minimizing any service disruptions.

By applying these techniques with the industry’s leading storage management software, the File Server Edition turnscommodity hardware into high performance, industrial-strength file servers while decreasing administrative burdeninvolved in maintaining and growing those systems.

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© 2000 VERITAS Software Corp. All rights reserved. VERITAS is a registered trademark ofVERITAS Software Corporation in the US and other countries. The VERITAS logo, BusinessWithout Interruption and VERITAS File Server Edition, File System, Volume Manager,QuickLog are trademarks of VERITAS Software Corporation in the US and other countries.Other product names mentioned herein may be trademarks and/or registered trademarks oftheir respective companies. Printed in USA. March 2000.