Migrating Services That Use Hitachi TrueCopy Data Replication With a Switchover

Perform a switchover of a Hitachi TrueCopy protection group when you want to migrate services to the partner cluster in an orderly fashion. A switchover consists of the following:

Application services are offline on the former primary cluster, cluster-paris.

For a reminder of which cluster is cluster-paris, see Figure 2–1.
The data replication role is reversed and now continues to run from the new primary, cluster-newyork, to the former primary, cluster-paris.
Application services are brought online on the new primary cluster, cluster-newyork.

Validations That Occur Before a Switchover

When a switchover is initiated by using the geopg switchover command, the data replication subsystem runs several validations on both clusters. The switchover is performed only if the validation step succeeds on both cluster.

First, the replication subsystem checks that the Hitachi TrueCopy device group is in a valid aggregate device group state. Then, it checks that the local device group states on the target primary cluster, cluster-newyork, are 23, 33, 43, or 53. The local device group state is returned by the pairvolchk -g device-group-name -ss command. These values correspond to a PVOL_PAIR or SVOL_PAIR state. The Hitachi TrueCopy command given on the new primary cluster, cluster-newyork, are described in the following table.

Table 11–1 Hitachi TrueCopy Switchover Validations on the New Primary Cluster


Aggregate Device Group State	Valid Device Group State on Local Cluster	Hitachi TrueCopy Switchover Command Issued on `cluster-newyork`
SMPL	None	None
Regular primary	23, 43	No command is issued, because the Hitachi TrueCopy device group is already in the `PVOL_PAIR` state.
Regular secondary	33, 53	`horctakeover -g dg [-t]` The`-t` option is given when the `fence_level` of the Hitachi TrueCopy device group is `async`. The value is calculated as 80% of the protection group's `Timeout` property. For example, if the protection group has a `Timeout` of 200 seconds, the value of `-t` used in this command will be 80% off 200 seconds, or 160 seconds.
Takeover primary	None	None
Takeover secondary	None	None

Results of a Switchover From a Replication Perspective

After a successful switchover, at the data replication level the roles of the primary and secondary volumes have been switched. The pre-switchover PVOL_PAIR volumes become the SVOL_PAIR volumes. The pre-switchover SVOL_PAIR volumes become the PVOL_PAIR volumes. Data replication will continue from the new PVOL_PAIR volumes to the new SVOL_PAIR volumes.

The Local-role property of the protection group is also switched, regardless of whether the application could be brought online on the new primary cluster as part of the switchover operation. On the cluster on which the protection group had a Local role of Secondary, the protection group's Local-role becomes Primary. On the cluster on which the protection group had a Local-role of Primary, the protection group's Local-role becomes Secondary.

How to Switch Over a Hitachi TrueCopy Protection Group From Primary to Secondary

Before You Begin

For a successful switchover, data replication must be active between the primary and the secondary clusters and data volumes on the two clusters must be synchronized.

Before you switch over a protection group from the primary cluster to the secondary cluster, ensure that the following conditions are met:

The Sun Cluster Geographic Edition software is up and running on the both clusters.
The secondary cluster is a member of a partnership.
Both cluster partners can be reached.
The protection group is in the OK state.

Caution –

If you have configured the Cluster_dgs property, only applications that belong to the protection group can write to the device groups specified in the Cluster_dgs property.

Steps

Log in to one of the cluster nodes.

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.

Initiate the switchover.

The application resource groups that are a part of the protection group are stopped and started during the switchover.
# geopg switchover [-f] -m new-primary-cluster protection-group-name
-f

Forces the command to perform the operation without asking you for confirmation.

-m new-primary-cluster

Specifies the name of the cluster that is to be the new primary cluster for the protection group.

protection-group-name

Specifies the name of the protection group.

Example 11–1 Forcing a Switchover From Primary to Secondary

The following example illustrates how to perform a switchover to the secondary cluster.

# geopg switchover -f -m cluster-newyork tcpg