HP 3PAR Operating System Software - Manual (Page 205)

creates snapshots of all the secondary virtual volumes that were previously synchronized a.
b.
resynchronizes the secondary virtual volume by sending only the differences between the
resynchronization snapshot and the current data in the primary virtual volume.
•
If a resynchronization snapshot does not exist, Remote Copy performs a full synchronization.
•
If the backup storage system is temporarily converted to a primary storage system (for example,
during disaster recovery or as part of planned downtime), Remote Copy:
a.
creates a snapshot on that system
b. uses this snapshot to resynchronize the natural primary storage system after the primary
system and the links are brought back up and Remote Copy resumes operations
Additional Information:
•
“Recovering from Disaster” (page 102)
•
“Error Handling” (page 207)
Snapshots in Asynchronous Periodic Mode
In asynchronous periodic mode, Remote Copy creates snapshots as part of normal operations.
Snapshots are used to locate the data written between two synchronizations.
Snapshots Taken during Initial Synchronization
During the initial synchronization, Remote Copy:
1.
takes a snapshot of the primary volume
2. sends that snapshot over to initialize the secondary volume
Snapshots Taken during Resynchronization
At the next scheduled resynchronization or whenever you issue the syncrcopy command, Remote
Copy:
1.
takes new snapshots of the secondary and primary volumes
2. sends the differences between the old primary snapshot and the new primary snapshot over
to resynchronize the secondary base volume
During resynchronization:
•
The secondary volume state is syncing.
•
Just as in synchronous mode, the secondary volume is not in a consistent state because the
updates are written by location order rather than by time order.
•
When the resynchronization completes, Remote Copy deletes the old snapshots on the primary
and the backup systems.
•
After resynchronization, the base volume on the backup storage system matches the new
snapshot on the primary storage system. The new snapshot on the primary system can now
be used in the next resynchronization operation.
Snapshots in Asynchronous Periodic Mode 205