Using Global Mirror for a planned failover and failback

Use this process to manage a planned failover involving two sites, which are referred to as local (or production) and remote (or recovery) sites, using Global Mirror.

During a planned outage, all storage units, servers, and networks are functional. Last and current states of all components are well-defined.

Examples for planned outages are system maintenance, disaster recovery tests, and training. The objective of the failover and failback procedures is to continue with consistent and current data (without any loss of transactions).

The procedure that is presented in this section makes the following assumptions:

All storage units (local and remote) are functional and accessible.
Applications are updating the primary volumes that are located at the local site.
Paths are created from the local to the remote site.
You have already created an environment to manage a planned outage.

Perform the following steps using the DS Storage Manager to begin the planned failover. You can also use the DS CLI.

Note: For details on individuals tasks, see the related topics section.

Quiesce host I/O that is updating the primary volumes that is located in the local site.
Check the status of Global Mirror to ensure that Global Mirror is in a good state and that a consistency group has formed successfully at the desired interval.
Wait until two consistency groups form successfully.
Pause Global Mirror and suspend the Global Copy pairs (A->B).
Create paths from the B volumes to the A volumes.
Perform recovery failover on the B volumes (B->A).
Perform the fast reverse restore process from the C volumes to the B volumes, selecting the Initiate background copy option.
Notes:
1. When you initiate the fast reverse restore process, Volume C becomes unusable.
2. There must be no I/O allowed to the B or C volumes during the fast reverse restore process.
Wait for the background copy to complete before continuing to the next step. The C to B FlashCopy relationship ends when the background copy completes.
Initiate the FlashCopy from Volume B back to Volume C. Ensure that you also select the Enable Change Recording and Inhibit writes to target volume options. This creates a backup copy of the consistency group before applications begin to update the B volumes.
Start the host I/O at the remote site on the B volumes. You will remain in production on the remote site in this configuration until you are ready to return production to the local site.
When you are ready to return production to the local site, perform recovery failback (B->A) to resynchronize the A volumes. The application at the remote site remains active.
After the resynchronize process has completed its first pass, quiesce the applications at your remote site so that the resynchronization can complete.
When the resynchronization has completed (no out-of-sync tracks), perform recovery failover and failback with Global Copy on Volume A to re-create the Volume A to Volume B Metro Mirror relationship.
Start the host I/O at the local site on the A volumes.
Resume the Global Mirror process.