Backup planning for geographic mirroring
Before implementing high availability based on geographic mirroring, you should understand and plan a backup strategy within this environment.
Before configuring any high-availability solution, assess your current backup strategy and make appropriate changes if necessary. Geographic mirroring does not allow concurrent access to the mirror copy of the independent disk pool, which has implications to performing remote backups. If you want to back up from the geographically mirrored copy, you must quiesce mirroring on the production system and suspend the mirrored copy with tracking enabled. Tracking allows for changes on the production to be tracked so that they can be synchronized when the mirrored copy comes back online. Then you must vary on the suspended "mirror" copy of the independent disk pool, perform the backup procedure, vary off "the suspended mirror copy" and then resume the independent disk pool to the original production host. This process only requires "partial data resynchronization" between the production and mirrored copies.
Your system is running exposed while doing the backups and when synchronization is occurring. It is also recommended that you suspend mirroring with tracking enabled, which speeds up the synchronization process. Synchronization is also required for any persistent transmission interruption, such as the loss of all communication paths between the source and target systems for an extended period of time. You can also use redundant communication paths to help eliminate some of those risks associated with a communication failure.
It is recommended that you should also use geographic mirroring in at least a three system, or logical partitions, where the production copy of the independent disk pool can be switched to another system at the same site that can maintain geographic mirroring.