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Sun Cluster Geographic Edition Data Replication Guide for Hitachi TrueCopy and Universal Replicator

Forcing a Takeover on a System That Uses Hitachi TrueCopy or Universal Replicator Data Replication

Perform a takeover when applications need to be brought online on the secondary cluster regardless of whether the data is completely consistent between the primary volume and the secondary volume. The information in this section assumes that the protection group has been started.

The following steps occur after a takeover is initiated:

For details about the possible conditions of the primary and secondary cluster before and after takeover, see Appendix C, Takeover Postconditions, in Sun Cluster Geographic Edition System Administration Guide.

The following sections describe the steps you must perform to force a takeover by a secondary cluster.

Validations That Occur Before a Takeover

When a takeover is initiated by using the geopg takeover command, the data replication subsystem runs several validations on both clusters. These steps are conducted on the original primary cluster only if the primary cluster can be reached. If validation on the original primary cluster fails, the takeover still occurs.

First, the replication subsystem checks that the Hitachi TrueCopy or Universal Replicator device group is in a valid aggregate device group state. Then, the replication subsystem checks that the local device group states on the target primary cluster, cluster-newyork, are not 32 or 52. These values correspond to a SVOL_COPY state, for which the horctakeover command fails. The Hitachi TrueCopy or Universal Replicator commands that are used for the takeover are described in the following table.

Table 3–2 Hitachi TrueCopy or Universal Replicator Takeover Validations on the New Primary Cluster

Aggregate Device Group State 

Valid Local State Device Group State 

Hitachi TrueCopy or Universal Replicator Takeover Commands That Are Run on cluster-newyork

SMPL 

All 

No command is run. 

Regular primary 

All 

No command is run. 

Regular secondary 

All Regular secondary states except 32 or 52 

For a list of Regular secondary states, refer to Table 2–1 and Table 2–2.

horctakeover -S -g dg [-t]

The-t option is given when the fence_level of the Hitachi TrueCopy or Universal Replicator device group is async. The value is calculated as 80% of the Timeout property of the protection group. For example, if the protection group has a Timeout of 200 seconds, the value of -t used in this command will be 80% of 200 seconds, or 160 seconds.

Takeover primary 

All 

No command is run. 

Takeover secondary 

All 

pairsplit -R-g dg pairsplit -S-g dg

Results of a Takeover From a Replication Perspective

From a replication perspective, after a successful takeover, the Local-role property of the protection group is changed to reflect the new role, it is immaterial whether the application could be brought online on the new primary cluster as part of the takeover operation. On cluster-newyork, where the protection group had a Local-role of Secondary, the Local-role property of the protection group becomes Primary. On cluster-paris, where the protection group had a Local-role of Primary, the following might occur:

If the takeover is successful, the applications are brought online. You do not need to run a separate geopg start command.

Caution – Caution –

After a successful takeover, data replication between the new primary cluster, cluster-newyork, and the old primary cluster, cluster-paris, is stopped. If you want to run a geopg start command, you must use the -n option to prevent replication from resuming.

ProcedureHow to Force Immediate Takeover of Hitachi TrueCopy or Universal Replicator Services by a Secondary Cluster

Before You Begin

Before you force the secondary cluster to assume the activity of the primary cluster, ensure that the following conditions are met:

  1. Log in to a node in the secondary cluster.

    You must be assigned the Geo Management RBAC rights profile to complete this procedure. For more information about RBAC, see Sun Cluster Geographic Edition Software and RBAC in Sun Cluster Geographic Edition System Administration Guide.

  2. Initiate the takeover.


    # geopg takeover [-f] protectiongroupname
    -f

    Forces the command to perform the operation without your confirmation

    protectiongroupname

    Specifies the name of the protection group

Example 3–2 Forcing a Takeover by a Secondary Cluster

This example forces the takeover of tcpg by the secondary cluster cluster-newyork.

The phys-newyork-1 cluster is the first node of the secondary cluster. For a reminder of which node is phys-newyork-1, see Example Sun Cluster Geographic Edition Cluster Configuration in Sun Cluster Geographic Edition System Administration Guide.


phys-newyork-1# geopg takeover -f tcpg
Next Steps

For information about the state of the primary and secondary clusters after a takeover, see Appendix C, Takeover Postconditions, in Sun Cluster Geographic Edition System Administration Guide.