Huawei UltraPath Technical White Paper.pdf

download Huawei UltraPath Technical White Paper.pdf

of 12

Transcript of Huawei UltraPath Technical White Paper.pdf

  • 5/24/2018 Huawei UltraPath Technical White Paper.pdf

    1/12

    Doc. code

    UltraPath Technical

    White Paper

    Issue 01

    Date 2012-04-20

    HUAWEI TECHNOLOGIES CO., LTD.

  • 5/24/2018 Huawei UltraPath Technical White Paper.pdf

    2/12

    UltraPath Technical White Paper

    CONFIDENTIA

    L

    2013-7-30Copyright Huawei Technologies Co., Ltd.2012. All rights reserved P 2 Total 12

    Copyright Huawei Technologies Co., Ltd. 2012. All rights reserved.

    No part of this document may be reproduced or transmitted in any form or by any means

    without prior written consent of Huawei Technologies Co., Ltd.

    Trademarks and Permissions

    and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd.

    All other trademarks and trade names mentioned in this document are the property of their

    respective holders.

    Notice

    The purchased products, services and features are stipulated by the contract made between

    Huawei and the customer. All or part of the products, services and features described in this

    document may not be within the purchase scope or the usage scope. Unless otherwisespecified in the contract, all statements, information, and recommendations in this document

    are provided "AS IS" without warranties, guarantees or representations of any kind, either

    express or implied.

    The information in this document is subject to change without notice. Every effort has been

    made in the preparation of this document to ensure accuracy of the contents, but all

    statements, information, and recommendations in this document do not constitute the

    warranty of any kind, express or implied.

    Huawei Technologies Co., Ltd.

    Address: Huawei Industrial Base

    Bantian, Longgang

    Shenzhen 518129People's Republic of China

    Website: http://www.huawei.com

    Email: [email protected]

    http://www.huawei.com/http://www.huawei.com/mailto:[email protected]:[email protected]:[email protected]://www.huawei.com/
  • 5/24/2018 Huawei UltraPath Technical White Paper.pdf

    3/12

    UltraPath Technical White Paper

    CONFIDENTIA

    L

    2013-7-30Copyright Huawei Technologies Co., Ltd.2012. All rights reserved P 3 Total 12

    Chapter 1 Overview

    1.1 Single Point Failure

    The single point failure indicates that any failure on the network can lead to the

    breakdown of the entire network. According to this definition, the single point

    failure may occur to:

    1 Path between the external network and the application server (AS)

    2 As

    3 Path between the AS and the controller

    4 Controller

    5 Path between the controller and disks

    6 Disks

    To prevent the single point failure, the highly-reliable system performs redundant

    backup for devices that are possible to meet the single point failure. The

    redundant backup is performed in interconnected networking to achieve highest

    reliability and performance.

    The multi-path technology can ensure the reliability of redundant paths. If one

    path is unavailable and cannot meet requirements on specified performance, the

    multi-path technology can automatically and transparently transmit the I/O flow to

    another available path. In this way, the I/O flow can be effectively and reliably

    transmitted. SeeFigure 1-11.

    Figure 1-1 Multi-path networking

  • 5/24/2018 Huawei UltraPath Technical White Paper.pdf

    4/12

    UltraPath Technical White Paper

    CONFIDENTIA

    L

    2013-7-30Copyright Huawei Technologies Co., Ltd.2012. All rights reserved P 4 Total 12

    1.2 Introduction to the OceanStor UltraPath

    The OceanStor UltraPath is the first self-developed multi-path software in China.

    It is based on the host driver to control access to storage devices, thus achieving

    pathing between the host and storage devices and improving path reliability and

    performance between the host and storage devices. The OceanStor UltraPath

    provides easy management of paths between the host and storage devices and

    provides a simple, fast, and efficient management solution.

    Chapter 2 Work Principle

    In a highly reliable system, redundant backup can be performed for the single

    point failure, but problems may occur without the installation of the UltraPath.

    Illusion: When multiple paths are connected, multiple real mapped LUNs are seen

    on the AS, thus creating a false appearance.

    Risk: The operating system (OS) thinks the two disks are independent, thus

    destroying the data or leading to I/O error.

    No redundancy: The OS cannot decide when and how to use the redundant path.

    Waste of resources: The OS cannot use the redundant path to balance load.

  • 5/24/2018 Huawei UltraPath Technical White Paper.pdf

    5/12

    UltraPath Technical White Paper

    CONFIDENTIA

    L

    2013-7-30Copyright Huawei Technologies Co., Ltd.2012. All rights reserved P 5 Total 12

    As shown in the left figure of Figure 2-1, when a LUN is mapped to the host

    through two HBAs, two mappings are seen on the host. When the two LUNs are

    read or written, data conflict occurs.

    Figure 2-1 Situations with the UltraPath and without the UltraPath

    When the UltraPath is installed, redundant devices can be shielded, thus avoiding

    illusion. A new device is created to correspond to multiple paths. As shown in the

    right figure ofFigure 2-1,the OS can see a real disk VDisk through the UltraPath.

    The application can directly access the disk virtualized by the UltraPath and the

    disk corresponds to multiple paths. In this way, data conflict is avoided.

    The UltraPath can achieve failover and load balance between servers and arrays.

    If a LUN is connected to multiple paths, the UltraPath can automatically choose

    the optimal path. When the current path is unavailable, other redundant paths can

    be used, thus avoiding service interruption caused by the single point failure.

    When multiple optimal paths are available, static and dynamic load balance on

    the multiple paths can be achieved, thus greatly improving I/O performance.

    Chapter 3 Technical Feature

    3.1 Creating Virtual Devices

    For users, it is dangerous to perform any operation on any redundant LUN

    (actually the LUN on the same array). When multiple paths are connected, each

    LUN on the array is mapped for many times. It means that a LUN on the same

  • 5/24/2018 Huawei UltraPath Technical White Paper.pdf

    6/12

    UltraPath Technical White Paper

    CONFIDENTIA

    L

    2013-7-30Copyright Huawei Technologies Co., Ltd.2012. All rights reserved P 6 Total 12

    array has multiple images in the OS. Any operation on the LUN can arouse data

    access conflict.

    The UltraPath can hide the redundant LUN that is mapped for many times and

    disenable any operation on the redundant LUN. Users can see and use the virtual

    LUN created by the UltraPath. The virtual LUN is an integration of the information

    about the redundant LUN. When users operate the virtual LUN, the UltraPath

    hides the choosing and controlling of actual paths by the UltraPath.

    The virtual LUN created by the UltraPath is classified into two types:

    1. In the AIX OS, only one OS device node is reserved for each redundant device.

    The other OS device nodes are hidden.

    2. In the Windows OS and the Linux OS, use the UltraPath to create a new device

    node. The UltraPath can name the new device node in a recognizable method.

    The process of creating a virtual LUN is transparent to upper layer applications

    and does not destroy original data on the LUN, thus ensuring data correctness

    and operation availability.

    3.2 Automatically Choosing a Optimal Path

    Automatically choosing a optimal path indicates choosing the best path between

    the AS and the storage system.

    Each LUN is owned by an owning controller. The features of arrays decide that

    the quickest speed to access the LUN is through the owning controller. The pathconnected to the owning controller is the optimal path. The UltraPath can obtain

    the information about the owning controller that owns the LUN and choose one or

    multiple paths connected to the controller to perform I/O operations, thus

    achieving the quickest I/O speed. As shown in , VDisk isowned by controller A. The UltraPath will first choose the path connected to

    controller A as the optimal path.

    The UltraPath will first choose the optimal path as the current path. When the

    optimal path fails, the driver can automatically perform failover. When the optimal

    path is recovered, the driver can restore the current path to the optimal path.

    3.3 Failover

    When the currently used path fails, the UltraPath will automatically switch the

    services to other redundant paths. The switch process is transparent to the upper

    layer applications without human interference, thus avoiding service interruption

    caused by the single point failure.

    When detecting that the currently used path fails, the UltraPath perform failback

    to switch the services from the faulty path to the normal optimal path. The driver

    will run without interruption. When failover occurs between the host and the

  • 5/24/2018 Huawei UltraPath Technical White Paper.pdf

    7/12

    UltraPath Technical White Paper

    CONFIDENTIA

    L

    2013-7-30Copyright Huawei Technologies Co., Ltd.2012. All rights reserved P 7 Total 12

    switch, HBA 1 is automatically switched to HBA 2. When failover occurs between

    the device and the switch, the faulty path is automatically switched to another

    path. SeeFigure 3-11.

    Figure 3-1 HBA-level failover and target-level failover

    3.4 Failback

    When the faulty path on which the services are switched to other paths is

    recovered, the UltraPath will automatically switch back to the recovered path. The

    switch process is transparent to the upper layer applications. The UltraPath can

    detect paths periodically and perform failback when the faulty path is recovered.

    The periods can be set through configuration files.

    The failover and failback function of the UltraPath can automatically detect

    inactive paths periodically, detect the path fault, and recover the fault. When a

    path fails, the UltraPath performs failover. When the UltraPath detects that the

    faulty path is recovered, it performs failback. The failover and failback operation

    can be performed without human interference. The services of users can still be

    kept online, thus optimizing the performance and maximizing storage assets.

    3.5 I/O Load Balance

    When there are more than two optimal paths connected from the AS to the

    storage system, you can achieve static and dynamic load balance.

    Static load balance indicates that when a LUN has multiple I/Os, the UltraPath

    chooses the optimal paths to send I/Os to different paths through Round-Robin in

  • 5/24/2018 Huawei UltraPath Technical White Paper.pdf

    8/12

    UltraPath Technical White Paper

    CONFIDENTIA

    L

    2013-7-30Copyright Huawei Technologies Co., Ltd.2012. All rights reserved P 8 Total 12

    turn, that is, send I/Os to optimal paths in turn to reduce the I/O load on a single

    path.

    Compared with static load balance, dynamic load balance can dynamically

    choose to send I/Os to the path that has the smallest amount of I/Os for better

    performance, especially when the performance of two paths is inconsistent due to

    the performance of HBAs or other reasons. Dynamic load balance is classified

    into minimum queue depth load balance and minimum task load balance. For

    minimum queue depth load balance, the UltraPath chooses the path that has

    finished the maximum number of I/Os from the optimal paths. For minimum task

    load balance, the UltraPath chooses the path that sends the minimum number of

    I/Os from the optimal paths.

    3.6 Dynamically Sensing a LUN

    When the storage system changes (increase or decrease) the number of LUNs

    mapped to the AS, the UltraPath can update the changing number of LUNs

    online.

    The UltraPath can dynamically manage the LUNs added to or deleted from the

    host. When you add or delete one or multiple LUN mappings on the host without

    shutting down the server or interrupting services, the UltraPath can dynamically

    sense the information about the LUN and update related information in the driver.

    3.7 Availability of Application Software

    1. Supporting cluster software

    The UltraPath is transparent to the upper-layer application software, and can

    achieve load balance in cluster nodes by using the cluster software.

    The UltraPath supports the mainstream cluster software, such as MSCS, VCS,

    HACMP, and Oracle RAC. In the cluster networking, the UltraPath works as a

    bridge between the cluster software and arrays, thus optimizing the cluster

    networking.

    The UltraPath converts the SCSI-2 command sent by the host to the SCSI-3

    command, thus enabling cluster nodes to achieve load balance, failover, and

    failback. Frequent switch of cluster nodes is avoided, that is, when a single path

    on the primary node fails, another redundant path on the node is switched

    through the failover function, thus ensuring the continuance of applications on the

    node and avoiding the high price paid for switching cluster nodes for the single

    point failure in clusters.

    2. Supporting database

  • 5/24/2018 Huawei UltraPath Technical White Paper.pdf

    9/12

    UltraPath Technical White Paper

    CONFIDENTIA

    L

    2013-7-30Copyright Huawei Technologies Co., Ltd.2012. All rights reserved P 9 Total 12

    The UltraPath supports the mainstream database software, such as Oracle, DB2,

    MySQL, Sybase, and Informix.

    3.8 Applicability and Correctness

    The UltraPath is installed on a server that supports FC, SAS, and iSCSI host

    interfaces. The UltraPath supports three host platforms: Windows, Linux, and

    AIX.

    When the UltraPath switches paths and performs load balance during the I/O

    process, the UltraPath can ensure the correctness of I/O data, that is, path switch

    and load balance are transparent to the upper-layer I/Os.

    3.9 Expandable Architecture

    When the UltraPath is installed, on the base of destroying no customers' data,

    you can convert the single path networking to the multi-path networking or the

    single switch networking to the dual-switch networking.

    The UltraPath can achieve conversion.Original configurations on the storage

    arrays and the running service on the host are not affected. The UltraPath makes

    full use of redundant paths to improve storage usage and service running

    efficiency.

    Figure 3-2 Conversion from a single path to multi-path

    Figure 3-3 Conversion from a single switch to dual-switch

  • 5/24/2018 Huawei UltraPath Technical White Paper.pdf

    10/12

    UltraPath Technical White Paper

    CONFIDENTIA

    L

    2013-7-30Copyright Huawei Technologies Co., Ltd.2012. All rights reserved P 10 Total 12

    Chapter 4 Application Scenario

    4.1 Typical Networking

    The UltraPath can apply to any networking with the AS and storage arrays that

    are installed with OSs (Windows, Linux, and AIX). The UltraPath provides

    multi-path solution for the AS to access storage arrays, thus improving security,

    reliability, and maintainability of enterprise data storage.

    Figure 4-1 shows the single controller, single HBA, and direct networking. In this

    way, the single path failure can be avoided. When one path fails, the services on

    the faulty path can be quickly switched to another path.

    Figure 4-1 Single controller, single HBA, and direct networking

  • 5/24/2018 Huawei UltraPath Technical White Paper.pdf

    11/12

    UltraPath Technical White Paper

    CONFIDENTIA

    L

    2013-7-30Copyright Huawei Technologies Co., Ltd.2012. All rights reserved P 11 Total 12

    Figure 4-2 shows the single switch and dual-switch networking. The UltraPath

    achieves path redundancy on a single storage controller, that is, multiple optimal

    paths can be chosen to achieve I/O load balance, thus greatly increasing I/O

    efficiency.

    Figure 4-2 Single switch and dual-switch networking

    Figure 4-3 Cluster dual-switch networking

  • 5/24/2018 Huawei UltraPath Technical White Paper.pdf

    12/12

    UltraPath Technical White Paper

    CONFIDENTIA

    L

    2013-7-30Copyright Huawei Technologies Co., Ltd.2012. All rights reserved P 12 Total 12

    When the cluster networking adopts switches, failover and failback can be

    achieved on a single node in the cluster and I/O load balance of multiple paths on

    a single node can also be achieved, as shown inFigure 4-3.