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Sun Cluster Geographic Edition System Administration Guide

ProcedureHow to Perform a Failback-Takeover on a System That Uses Hitachi TrueCopy Replication

Use this procedure to restart an application on the original primary cluster, cluster-paris and use the current data on the original primary cluster. Any updates that occurred on the secondary cluster, cluster-newyork, while it was acting as primary are discarded.

Note –

Conditionally, you can resume using the data on the original primary, cluster-paris. You must not have replicated data from the new primary, cluster-newyork, to the original primary cluster, cluster-paris, at any point after the takeover operation on cluster-newyork. To prevent data replication between the new primary and the original primary, you must have used the -n option any time you used the geopg start command.

Before You Begin

Before you begin the failover-takeover operation, the clusters have the following roles:

Steps

  1. Resynchronize the original primary cluster, cluster-paris, with the original secondary cluster, cluster-newyork.

    cluster-paris forfeits its own configuration and replicates the cluster-newyork configuration locally.

    1. On cluster-paris, resynchronize the partnership.


      # geops update partnership-name
      partnership-name

      Specifies the name of the partnership

      Note –

      You need to perform this step only once, even if you are performing a failback-takeover for multiple protection groups.

      For more information about synchronizing partnerships, see Resynchronizing a Partnership.

    2. Put the Hitachi TrueCopy device group, devgroup1, in the SMPL state.

      Use the pairsplit commands to put the Hitachi TrueCopy device groups that are in the protection group on both cluster-paris and cluster-newyork in the SMPL state. The pairsplit command you use depends on the pair state of the Hitachi TrueCopy device group. The following table gives some examples of the command you need to use on cluster-paris for some typical pair states.

      Pair State on cluster-paris

      Pair State on cluster-newyork

      pairsplit Command Used on cluster-paris

      PSUS or PSUE

      SSWS

      pairsplit -R -g dgname

      pairsplit -S -g dgname

      SSUS

      PSUS

      pairsplit -S -g dgname

      For more information about the pairsplit commands, see the Sun StorEdge SE 9900 V Series Command and Control Interface User and Reference Guide.

      If the command is successful, the state of devgroup1 is given in the output of the pairdisplay command as follows:


      phys-paris-1# pairdisplay -g devgroup1
Group PairVol(L/R) (Port#,TID,LU),Seq#,LDEV#,P/S,Status,Fence,Seq#,P-LDEV# M 
devgroup1 pair1(L) (CL1-A , 0, 1) 12345   1..SMPL ----  ----,-----  ----   - 
devgroup1 pair1(R) (CL1-C , 0, 20)54321 609..SMPL ----  ----,-----  ----   - 
devgroup1 pair2(L) (CL1-A , 0, 2) 12345   2..SMPL ----  ----,-----  ----   - 
devgroup1 pair2(R) (CL1-C , 0,21) 54321 610..SMPL ----  ----,-----  ----   -

      .

    3. On cluster-paris, resynchronize each protection group.

      Because the local role of the protection group on cluster-newyork is now primary, this step ensures that the local role of the protection group on cluster-paris is secondary.


      # geopg update protection-group-name
      protection-group-name

      Specifies the name of the protection group

      For more information about resynchronizing protection groups, see How to Resynchronize a Protection Group.

  2. On cluster-paris, validate the cluster's configuration for each protection group.


    # geopg validate protection-group-name
    protection-group-name

    Specifies a unique name that identifies a single protection group

    For more information, see How to Validate a Hitachi TrueCopy Protection Group.

  3. On cluster-paris, activate each protection group in the secondary role without data replication.

    Because the protection group on cluster-paris has a role of secondary, the geopg start command does not restart the application on cluster-paris.


    # geopg start -e local -n protection-group-name
    -e local

    Specifies the scope of the command

    By specifying a local scope, the command operates on the local cluster only.

    -n

    Prevents the start of data replication at protection group startup

    Note –

    You must use the -n option.

    protection-group-name

    Specifies the name of the protection group

    For more information, see How to Activate a Hitachi TrueCopy Protection Group.

    Replication from cluster-newyork to cluster-paris is not started, because the -n option is given on cluster-paris.

  4. On cluster-paris, initiate a takeover for each protection group.


    # geopg takeover [-f] protection-group-name
    -f

    Forces the command to perform the operation without your confirmation

    protection-group-name

    Specifies the name of the protection group

    For more information about the geopg takeover command, see How to Force Immediate Takeover of Hitachi TrueCopy Services by a Secondary Cluster.

    The protection group on cluster-paris now has the primary role, and the protection group on cluster-newyork has the role of secondary. The application services are now online on cluster-paris.

  5. On cluster-newyork, activate each protection group.

    At the end of step 4, the local state of the protection group on cluster-newyork is Offline. To start monitoring the local state of the protection group, you must activate the protection group on cluster-newyork.

    Because the protection group on cluster-newyork has a role of secondary, the geopg start command does not restart the application on cluster-newyork.


    # geopg start -e local [-n] protection-group-name
    -e local

    Specifies the scope of the command

    By specifying a local scope, the command operates on the local cluster only.

    -n

    Prevents the start of data replication at protection group startup

    If you omit this option, the data replication subsystem starts at the same time as the protection group.

    protection-group-name

    Specifies the name of the protection group

    For more information about the geopg start command, see How to Activate a Hitachi TrueCopy Protection Group.