HP 3PAR Operating System Software - Manual (Page 204)

Snapshots in Synchronous Mode
In synchronous mode, Remote Copy creates snapshots only when:
•
an error occurs
•
disaster recovery is in process
•
a volume group is manually stopped
Snapshots and Initial Synchronization Failure
If a failure occurs during the initial (and therefore full) synchronization of a virtual volume:
•
Remote Copy does not create a snapshot of that volume.
•
After you recover the system and restart Remote Copy, Remote Copy performs another initial
(full) synchronization of the volume.
Snapshots and Resynchronization
During resynchronization:
•
The secondary volume state is syncing.
•
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 snapshots on the primary
and the backup systems.
NOTE: For more information on deleted snapshots and space re-allocation, see “How CPGs
Allocate Space for Snapshots” (page 187) .
Snapshots and Resynchronization Failure
•
If the primary system fails during a resynchronization, the secondary base volumes are left in
an inconsistent state, but the snapshots of the secondary volumes are left behind and not
deleted.
•
After you recover the primary system, the next resynchronization brings the secondary volumes
back in synchronization with the primary volumes.
•
If the primary system fails during a resynchronization and you need to use the backup system
to access data, you must issue failover commands. For more information, see
“Recovering
from Disaster” (page 102) .
Snapshots Taken before or during Disaster Recovery
If the Backup System Fails
If the backup system fails, or all communication links to the backup system fail, the primary system:
•
stops the replication of all volume groups
•
takes snapshots of all volumes that were completely synchronized
If the Primary System Fails
When Remote Copy restarts after a primary system failure (either manually using the
startrcopygroup
command or via the auto_recover policy), Remote Copy first looks for a
valid resynchronization snapshot for each virtual volume.
•
If a resynchronization snapshot exists, Remote Copy:
204 Remote Copy Snapshots