HP 3PAR Operating System Software - Manual (Page 127)

Considerations for Setting the Synchronization Period
CAUTION: When you set the synchronization period, you must allow sufficient time for the volume
group to complete synchronization. If you specify too small a time span between synchronizations,
the volume group might continuously synchronize.
The minimum synchronization period supported by remote copy is five minutes; the maximum is
one year.
Select a synchronization period based on the tolerance for data concurrency; in other words, the
amount of delay that can be tolerated before the backup system is updated.
Because resynchronization involves creating and deleting multiple snapshots, select a synchronization
period that is long enough to allow the previous resynchronization to complete. For more
information, see
“Resynchronization” (page 125) .
NOTE: The network link used for replication must be sufficiently large to ensure that all delta
data can be transmitted within the specified synchronization interval.
The resynchronization schedule starts its countdown from the current resynchronization start time.
Therefore, if a resynchronization is delayed, the next resynchronization starts after the interval
specified as the synchronization period.
For example, if you set the synchronization period to 10 minutes, and one resynchronization begins
at 1 pm but takes 12 minutes to complete, the next resynchronization begins around 1:12 pm. If
that resynchronization takes only 2 minutes to complete (which is within the 10 minute interval),
the next resynchronization begins at 1:22, 10 minutes after the previous resynchronization.
Synchronous Mode Volume Groups
Full Synchronization
If the primary volume was never successfully synchronized, HP 3PAR Remote Copy performs a full
synchronization.
Resynchronization
To resynchronize synchronous mode volume groups, HP 3PAR Remote Copy copies the I/O directly
from the primary base volume.
For more information, see “Volume Group Modes” (page 120) .
When synchronous mode volume groups are stopped, HP 3PAR Remote Copy creates snapshots
of the volume groups. When these volume groups are restarted, HP 3PAR Remote Copy uses the
snapshots to resynchronize the primary and secondary volume groups.
For more information, see “Remote-Copy Snapshots” (page 270) .
Synchronization 127