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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).
Creating an eDevLUN With Masquerading Properties

Creating an eDevLUN With Masquerading Properties

After creating an eDevLUN with masquerading properties in a storage pool of the local storage system, you can set up a mapping relationship between the eDevLUN and an application server without interrupting services and use the eDevLUN to read data from and write data into an external LUN.

Prerequisites

  • The remote LUNs mapped by the heterogeneous storage system have been added to the LUN list by automatic scanning.
  • External LUNs are in normal state.
  • Number of LUNs (including local LUNs and eDevLUNs) in a storage pool = Available capacity of the storage pool/512 MB. Before creating an eDevLUN, make an appropriate plan to ensure that the storage pool has sufficient capacity for the eDevLUN.
    • If you need to configure one of the remote replication, SmartMigration, HyperMirror, snapshot, and HyperMetro features for an eDevLUN, you must reserve a certain amount of capacity in the local storage pool for storing metadata generated by that feature. Reserved capacity = External LUN capacity x 5‰.
    • If you need to configure two or more of the remote replication, SmartMigration, HyperMirror, snapshot, and HyperMetro features for an eDevLUN, you must reserve a certain amount of capacity in the local storage pool. Reserved capacity = External LUN capacity x 1%.
    • If you want to configure HyperSnap and HyperReplication/A for eDevLUNs, reserve some space in the local storage pool to save copy-on-write (COW) data. The reserved capacity ranges from 20% to 30% of the external LUN capacity.
    • If you want to configure HyperReplication/S and HyperMetro for eDevLUNs, reserve some space in the local storage pool to save incremental data generated after replication fault occurs. The reserved capacity is 10% of the external LUN capacity.
  • The OceanStor 2200 V3/2600 V3 storage system does not allow the eDevLUNs with masquerading properties to be created for thin LUNs in the heterogeneous storage system and does not support online takeover of the eDevLUNs.
  • If the vStorage APIs for Array Integration (VAAI) or asymmetrical logical unit access (ALUA) function is enabled on the external LUNs of the heterogeneous storage system, the OceanStor 2200 V3/2600 V3 storage system does not allow the eDevLUNs with masquerading properties to be created for the external LUNs and does not support online takeover of the eDevLUNs.

Context

  • For a cluster configured with SCSI-3 and SCSI-2 reservation, only basic masquerading is supported for online takeover.
  • By default, the write policy of an eDevLUN whose masquerading properties are configured is write through. After a masqueraded eDevLUN is created, you cannot modify its write policy. The write policy can be modified only after you execute CLI commands to enable the local storage system to take over the heterogeneous storage system.
  • After a masqueraded eDevLUN is created, you can configure value-added features for it only after an online takeover is completed.

Precautions

After creating an eDevLUN for an external LUN, do not map the external LUN to other hosts or storage systems to avoid data inconsistency.

Procedure

  1. Log in to OceanStor DeviceManager.
  2. Choose Data Protection > Remote Device.
  3. Select the heterogeneous storage system where the external LUN resides. In the function pane, click the Remote LUN tab.
  4. Click Create eDevLUN.

    The Create eDevLUN dialog box is displayed.

  5. Create an eDevLUN with masquerading properties.
    1. Select a storage pool for the eDevLUN to be created.

      NOTE:
      • When eDevLUNs are created, the system automatically generates a default name for each eDevLUN. You can modify the default name.
      • If no storage pool is available, click Create to create a new storage pool.

    2. In LUN Masquerading, set the LUN masquerading type of the eDevLUN to be created to Basic masquerading or Extended masquerading.

      Do not select No Masquerading. Otherwise, the application server will regard the eDevLUN and external LUN as two different LUNs and writes different data to the two LUNs simultaneously, causing data inconsistency.

      LUN masquerading indicates that the identification information of the eDevLUNs in the local storage system is replaced by that of the external LUNs in the heterogeneous storage system so that the local storage system can take over the heterogeneous storage system. Table 3-8 lists the LUN masquerading types supported by the OceanStor 2200 V3/2600 V3 storage system.

      Table 3-8  LUN masquerading types

      LUN Masquerading Type

      Description

      Application Scenario

      Basic masquerading

      Basic masquerading replaces the basic information about an eDevLUN with the basic information (such as the WWN) about an external LUN when the LUN is taken over.

      OceanStor UltraPath V100R008C20 or later is installed on application servers. The storage systema SN can be queried using the UltraPath.

      Extended masquerading

      Extended masquerading replaces the basic information as well as extended LUN information including the SCSI protocol version and master controller when the LUN is taken over.

      • OceanStor UltraPath whose version is earlier than V100R008C20 or a piece of third-party multipathing software is installed on application servers.
      • UltraPath V100R008C20 or later is installed on application servers, and the storage system SN cannot be queried using the UltraPath.
      a: Models and versions of storage systems whose SNs cannot be queried using UltraPath.
      • S2300E/S2600
      • S5300/S5500/S5600
      • Dorado2100
      • Dorado5100 of versions earlier than V100R001C00SPC800 (excluding V100R001C00SPCa00 and V100R001C00SPCb00)
      • Dorado2100 G2 of versions earlier than V100R001C00SPC500 (excluding V100R001C00SPCa00 and V100R001C00SPCb00)
      • S2200T/S2600T/S5500T/S5600T/S5800T/S6800T of versions earlier than V1R5C00SPC400
      • S2200T/S2600T/S5500T/S5600T/S5800T/S6800T of versions earlier than V1R5C01SPC100

    3. In the list, select a remote LUN that you want to configure as an eDevLUN.
    4. Click Advanced and set the advanced properties of the eDevLUN. After setting the advanced properties, click OK to save the configuration and exit.

      Table 3-9 lists the advanced property parameters of an eDevLUN.

      Table 3-9  Advanced property parameters of an eDevLUN

      Parameter

      Description

      Value

      Read Policy

      Data read policy of an eDevLUN.

      The system supports the following three read policies:
      • Resident: Applies to services featuring random data access, ensuring that data can be cached as long as possible to improve the read hit ratio.
      • Default: Applies to regular services, striking a balance between the hit ratio and disk access performance.
      • Recycle: Applies to services featuring sequential data access, releasing cache resources for other services as soon as possible.

      [Value range]

      Possible values are Resident, Default, and Recycle.

      [Example]

      Default

      [Default value]

      Default

      Write Policy

      Data write policy of an eDevLUN.

      The system supports the following three write policies:
      • Resident: Applies to services featuring random data access, ensuring that data can be cached as long as possible to improve the write hit ratio.
      • Default: Applies to regular services, striking a balance between the hit ratio and disk access performance.
      • Recycle: Applies to services featuring sequential data access, releasing cache resources for other services as soon as possible.
      NOTE:

      If the change lun command is executed on the CLI to modify write_policy to write_through, this parameter becomes invalid.

      [Value range]

      Possible values are Resident, Default, and Recycle.

      [Example]

      Default

      [Default value]

      Default

      Prefetch Policy

      Read mode of an eDevLUN. When reading data, an eDevLUN prefetches required data from disks to the cache in advance according to a preset policy.
      • No prefetch: The storage system reads data according to the prefetch length specified in the I/O request.

        As a low read hit ratio may lead to performance degradation, No prefetch is recommended for random read services.

      • Intelligent prefetch: Intelligent prefetch analyzes whether the requested data is sequential. If it is, the data following the currently requested data is prefetched from disks to the cache to improve the cache hit ratio. If data is randomly read, no prefetch is performed and the required data is read from disks.

        This policy applies to a scenario where sequential reads and random reads coexist or a scenario where you cannot determine data reads to be sequential or random.

      • Constant prefetch: A constant length of data is read from disks every time when the cache reads data from the disks. The length is user-definable, ranging from 0 to 1024.

        This policy applies to sequential read applications with fixed-size data, for example, CRBT and multi-user streaming media VoD initiated by users at the same bit rate.

      • Variable prefetch: A variable length of data is read from disks every time when the cache reads data from disks. The length is a multiple of that specified in the host I/O request. The multiple is user-defined, ranging from 0 to 1024.

        This policy applies to sequential read applications with variable-size data or to multi-user concurrent read applications with an unknown data prefetch amount, for example, streaming media requests initiated by multiple users at different bit rates.

      [Value range]

      Possible values are No prefetch, Intelligent prefetch, and Constant prefetch, and Variable prefetch.

      [Example]

      Intelligent prefetch

      [Default value]

      Intelligent prefetch

  6. Confirm the creation of the eDevLUN.
    1. Click OK.

      The Execution Result dialog box is displayed indicating that the operation succeeded.

    2. Click Close.

Follow-up Procedure

An eDevLUN is created successfully if Used or Not of the corresponding remote LUN in the lower function pane is Yes. Choose Provisioning > LUN to view and manage the eDevLUN.

After taking over the eDevLUN with masquerading properties on line and before configuring value-added features for the eDevLUN, modify the write policy of the eDevLUN according to the following principles:
NOTE:

Method of modifying the write policy of an eDevLUN: Choose Provisioning > LUN. Select the eDevLUN whose write policy you want to modify and click Properties. On the Properties of LUN page that is displayed, click Advanced.

  • If you want to configure the HyperMirror feature for the eDevLUN, set the write policy of the eDevLUN to Write through and the write policy of the mirror copy generated on the local storage system to Write Back to ensure data consistency between the heterogeneous storage system and the local storage system.
  • If the SmartMigration feature is configured for the eDevLUN, set the write policy of the eDevLUN to Write through to ensure data consistency between the heterogeneous storage system and local storage system.
  • If the Snapshot, Remote Replication or HyperMetro is configured for the eDevLUN, set the write policy of the eDevLUN to Write back to ensure performance of the local storage system.
  • If HyperMirror and Snapshot are configured simultaneously for the eDevLUN, or HyperMirror and Remote Replication are configured simultaneously for it, set the write policy of the eDevLUN to Write back.
  • If no value-added feature is configured for the eDevLUN, you do not need to modify its write policy. Keep the default Write through policy.

After an eDevLUN is created, perform a rollback if you do not want to use the OceanStor 2200 V3/2600 V3 storage system for online takeover. For details, see Performing Rollback.

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Updated: 2018-12-29

Document ID: EDOC1000106155

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