Best Practices; Example Configuration; Achieving Nondestructive Rollback; Configuration For Nondestructive Rollback - HP StorageWorks P4000 User Manual

Best practices

Retain the most recent primary snapshots in the primary cluster
By keeping snapshots on your primary volume, you can quickly roll back a volume to a previous
snapshot without accessing off-site backups.
When you create a schedule for Remote Copy, specify the number of primary and remote snapshots
that you want to retain. You can retain primary snapshots to facilitate easy rollback of the primary
volume.
NOTE:
Retention of snapshots affects the amount of space that is used in the cluster of storage systems.
Balance the number of snapshots to retain with the amount of space you are willing to use. You
can still access remote snapshots or tape backups if you want to roll back to a snapshot that you
did not retain.
Retain remote snapshots in the backup location to facilitate fast recovery of backed-up data. If
you retain a number of remote snapshots after a tape backup is created, you can access the data
without going to the backup tape.

Example configuration

Retain three primary snapshots. This enables you to roll the primary volume back, yet it requires
a relatively small amount of space on the primary cluster.
Retain up to a week's worth of remote snapshots on the backup cluster.
For snapshots older than one week, go to the backup tape.

Achieving nondestructive rollback

As discussed in
a volume requires you to delete any snapshots that were created since the snapshot that you roll back
to. For example, suppose you created snapshots of a volume on Monday, Tuesday, and Wednesday.
On Thursday, if you roll the volume back to Monday's snapshot, then the snapshots from Tuesday
and Wednesday must be deleted first.
You can use Remote Copy to roll a volume back to an old snapshot without losing the interim snapshots.
Because Remote Copy creates two sets of snapshots—primary and remote snapshots—you can roll
a volume back to a snapshot and still retain the other set of snapshots.

Configuration for nondestructive rollback

To use remote snapshots for nondestructive rollback:
Create a remote snapshot schedule.
In the schedule, specify the same retention policy for the primary and remote snapshots. This ensures
that you have copies of the same number of snapshots in your primary and remote locations. Any
snapshots destroyed during rollback of one volume remain intact on the other volume. See an il-
lustration of a nondestructive rollback configuration in
52 Sample Remote Copy configurations
"Rolling back primary and remote volumes" on page 38, rolling a snapshot back to
Figure 18 on page 53.