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OceanStor 18500, 18800, and 18800F Storage System V100R001C30 Remote Replication Feature Guide 09

This document describes the remote replication feature, in terms of the implementation principle, application scenario, configuration process, and reference information.
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Creating a Consistency Group

Creating a Consistency Group

Remote replication can implement data backup and disaster recovery in the scenario where a host writes data to a single or multiple independent primary LUNs. However, remote replication cannot implement data backup and disaster recovery in the scenario where a host writes data to multiple dependent primary LUNs. A consistency group ensures data consistency of secondary LUNs of all remote replication pairs in the group at the same point in time (for example, the data of all secondary LUNs are the data copy of its primary LUN at 3:00 PM today), therefore ensures the data availability of primary LUNs after disaster recovery.

Prerequisites

  • The remote replication to be added into the consistency group must be split.
  • The Role of the remote replication to be added into the consistency group must be Primary.
  • The remote replications to be added into the consistency group must be from the same storage device.
  • The properties of the remote replication to be added into the consistency group must be the same as the properties of the consistency group. The properties are Replication Mode, Synchronization Method, Interval, Speed, and Recovery Policy.

Procedure

  1. Go to the dialog box for creating a consistency group.
    1. On the right navigation bar, click .

      The data protection page is displayed.

    2. In the left function pane, click Remote Replication.
    3. Click the Remote Replication Consistency Group tab.

      The consistency group management page is displayed.

    4. Click Create.

      The Create Remote Replication Consistency Group Wizard dialog box is displayed.

  2. Configure basic information about the consistency group.
    1. Name the remote replication in Name for identification.
    2. Describe the remote replication in Description.
    3. Click Next.
  3. Set the parameters of the consistency group, as described in Table 4-8.

    Table 4-8  Consistency group parameters

    Parameter

    Description

    Value

    Replication Mode

    Data replication mode of a consistency group. The value includes:

    • Synchronous: When data is written on a primary LUN, the write request is also sent to the secondary LUN. Only after the data is written on both the primary and secondary LUNs successfully, does the host receive a successful data write message. Synchronous mode ensures that the data on the primary LUN and secondary LUN synchronize in real-time.
    • Asynchronous: When data is written on a primary LUN successfully, the host receive a successful data write message. In the meanwhile, the primary site records the data difference between the written data and the secondary LUN. In the data synchronization later, only the different data the primary site records are synchronized to the secondary site, reducing the write latency of application server to the minimum.

    [Default value]

    Asynchronous

    Recovery Policy

    After the remote replication internal I/O error is rectified or the replication link is up, the consistency group automatically synchronizes data or not. The values include:
    • Manual: The consistency group enters the To be recovered state. You need to manually synchronize the data from the primary LUN to the secondary LUN.
    • Automatic: The consistency group enters the Synchronizing state. The system will automatically synchronize the data from the primary LUN to the secondary LUN.

    [Default value]

    Automatic

    Speed

    Rate of data synchronization of the consistency group. The values include:
    • Low: When the speed is set to low, remote replication will take a long time. This value is applicable to scenarios where the service load is heavy. The speed is normally from 0 to 5 MB/s.
    • Medium: When the speed is set to medium, remote replication will take relatively short period. This value is applicable to scenarios where the service load is heavy. The speed is normally from 10 to 20 MB/s.
    • High: When the speed is set to high, remote replication will take a short period. This value is applicable to scenarios where the service load is relatively light. The speed is normally from 50 to 70 MB/s.
    • Highest: When the speed is set to highest, remote replication will be complete in the shortest period. This value is applicable to scenarios where the service load is light. The speed is normally above 100 MB/s.

    [Default value]

    Medium

    Synchronization Method

    Mode of data synchronization of the consistency group. The values includes:

    • Manual: Synchronization is performed manually.
    • Timed wait when synchronization begins: The system starts timing as soon as the latest synchronization begins. When the time specified in Interval has elapsed, the system automatically starts to synchronize data between the primary LUN and secondary LUN again.
      NOTE:

      If the latest synchronization is still being executed after the time specified in Interval has elapsed, the data synchronization will start after the latest synchronization finishes.

    • Timed wait when synchronization ends: The system starts timing as soon as a synchronization ends. When the time specified in Interval has elapsed, the system starts to synchronize data again.

    [Default value]

    Manual

    NOTE:

    This parameter is available only when Replication Mode is set to Asynchronous.

    Interval

    Waiting time for the two synchronization methods, Timed wait when synchronization begins and Timed wait when synchronization ends.

    [Value range]

    • An integer ranging from 1 to 1440 (inclusive), when minutes is used as the unit.
    • An integer ranging from 3 to 59 (inclusive), when seconds is used as the unit.

    [Default value]

    60, when minutes is used as the unit.

    30, when seconds is used as the unit.

    NOTE:

    This parameter is available only when Synchronization Method is set to Timed wait when synchronization begins or Timed wait when synchronization ends.

  4. Add a remote replication pair to a consistency group.
    1. Select owning remote device of the secondary LUNs.
    2. In the Available Remote Replication Pairs area, select the remote replication pair you want to add.

      NOTE:

      The remote replication pair is only available when its running stauts is split, and its replication properties (Rate, Recovery policy and Synchronization Method) are consistent with the consistency group.

    3. Click Right Arrow to add the remote replication pair to the Selected Remote Replication Pairs area.

      NOTE:

      To remove a remote replication pair from the Selected Remote Replication Pairs area, click Left Arrow. The remote replication is moved to the Optional Remote Replication Pairs area.

    4. Click Next.
  5. Confirm the consistency group creation.
    1. View the configuration summary of the consistency group.
    2. Click Finish.

      The Results message box is displayed.

    3. Click Close.
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Updated: 2019-01-28

Document ID: EDOC1000077758

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