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OceanStor 2200 V3 and 2600 V3 Storage System V300R005 SmartVirtualization Feature Guide 07

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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Switching Over Host Paths

Switching Over Host Paths

Switch over host I/O paths to the paths between the local storage system and application servers. In this way, application servers can use eDevLUNs to deliver host I/Os to the heterogeneous storage system.

NOTE:

OceanStor UltraPath is used as an example here. If a piece of third-party multipathing software is installed on application servers, see the third-party multipathing software document to obtain commands.

The methods used to switch over host paths vary depending on different versions of OceanStor UltraPath installed on application servers.
  • If OceanStor UltraPath whose version is earlier than V100R008C20 is installed on an application server, remove the physical cables between the heterogeneous storage system and application server. The application server automatically switches over the I/O transfer path to the path between the local storage system and application server.
  • If OceanStor UltraPath V100R008C20 or later is installed on an application server, perform an operation specific to the network environment to switch I/Os to the path between the local storage system and the application server.
    • In a non-cluster environment or the cluster is running on AIX or Oracle RAC or is not configured with SCSI-3 and SCSI-2 reservation, run the start migration command on UltraPath CLI of the application server.
      The format of the start migration command is start migration vlun_id=ID direction={ source | target } rollback={ enable | disable }. Table 3-13 describes the command parameters.
      Table 3-13  Parameter description

      Parameter

      Description

      vlun_id=ID

      ID of the LUN scanned by the application server.

      direction={ source | target }

      Path switchover direction. Switch over I/Os to the target array or source array.
      • source: Switch over I/Os to the source array (heterogeneous storage system).
      • target: Switch over I/Os to the target array (local storage system).

      In this operation, switch over I/Os to the target array.

      rollback={ enable | disable }

      Enable or disable automatic rollback after an I/O switchover.
      • enable: Enable automatic rollback after an I/O switchover. If an online migration fails, I/Os can be switched back to the source array.
        NOTE:

        rollback can be set to enable only when direction is set to target.

      • disable: Disable automatic rollback after an I/O switchover. If an online migration fails, I/Os cannot be switched back to the source array.
    • In other type of cluster networking, perform the following operations on each host in the cluster:
      1. Run the start iosuspension vlun_id=<id> timeout=<value> command to suspend I/Os. This ensures consistency of registration and reserved information in the cluster during follow-up operations.

        You are advised to set <value> to 30, namely, 30 seconds, and ensure that follow-up operations can be completed within 30 seconds.

      2. Run the start migration vlun_id= direction=target rollback=enable command to switch I/Os to the path between the local storage system and the application server.
      3. To ensure that the operations in Migrating the Reserved Information and Confirming the Completion of the Host Path Switchover can be completed within 30 seconds, run the show vlun id=<id> command to check whether the I/O suspension period has expired.
        UltraPath CLI #2 >show vlun id=1
        =======================================================
        VLUN#1 Information
        =======================================================
        Disk : sdc
        Name : test_0001
        Status : Normal
        Capacity : 1.00GB
        Driver : Vendor-specific(DEFAULT)
        Product Name : XSG1
        Vendor Name : XXXXX
        Owning Controller : 0A
        Working Controller : 0A
        Num of Paths : 4
        LUN WWN : 648435a10077515b1a08cd540000002a
        Array Name : Huawei.Storage219.70
        Controller 0A
        Path 4 [1:0:4:2] (up-5) : Normal
        Path 10 [4:0:4:2] (up-13) : Normal
        Controller 0B
        Path 0 [1:0:0:2] (up-1) : Normal
        Path 8 [4:0:2:2] (up-9) : Normal
        Dev Lun ID : 42
        Manual IO Suspension : XXX
        -------------------------------------------------------
        In the command output, Manual IO Suspension indicates whether I/O suspension has timed out.
        • If Manual IO Suspension is Off, I/O suspension has timed out. Run the start migration vlun_id= direction=source rollback=disable command to switch the I/O path back to the path between the heterogeneous storage system and the application server, and perform 1 again.
        • If Manual IO Suspension is On (timeout/remain :{30000} seconds/{XXXXX} seconds) and XXXXX is smaller than 30000, I/O suspension has not timed out and you can perform follow-up operations.

Follow-up Procedure

  • For UltraPath earlier than V100R008C20, run show path on the application server to confirm that the status of all paths between the local storage system and the application server is normal. On DeviceManager, confirm that read and write I/Os exist. The host path is switched over successfully.

    After the host I/O path is switched over to the path between the local storage system and application server, remove the initiator that corresponds to the application server from the created hosts on the management interface of the heterogeneous storage system.

  • For UltraPath V100R008C20 and later versions, run show iostat vlun_id=? interval=? on the application server to check performance statistics about a specified LUN at a statistics interval. If read and write I/Os are generated, the host path is switched over successfully.
    After the host I/O path is switched over to the path between the local storage system and application server, perform the following operations:
    • Disconnect the heterogeneous storage system from the application server.
    • On the management interface of the heterogeneous storage system, remove the initiator that corresponds to the application server from the created hosts.
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Updated: 2018-12-29

Document ID: EDOC1000106155

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