HP 3PAR Remote Copy Software - Manual (Page 44)

2.28 Remote Copy Operation
Remote Copy User’s Guide InForm OS Version 2.3.1
2.9.2.2 Synchronous Mode Volume Groups
Rather than creating snapshots on the primary volume group for synchronous mode volume
groups, the I/O is taken directly from the base volume when synchronization begins.
Synchronous mode volume groups resynchronize automatically when they are stopped and
restarted. When stopped, the system takes snapshots that are used for resynchronization.
2.9.3 Resynchronization Period
In order for resynchronizations to be performed automatically with asynchronous periodic
mode volume groups, you must configure the synchronization period for the volume group.
There is no default synchronization period; it must be set using the setrcopygroup
command as described in Setting Remote Copy Volume Group Policies on page 4.4. This
command can be issued any time after the group is created, even after Remote Copy
operations have started for the group. When the resynchronization period is set for the
primary volume group, by default it is mirrored to the secondary.
The length of the synchronization period should be chosen based on the tolerance for data
concurrency (the amount of delay that can be tolerated in updating the backup storage
server).
The minimum synchronization period supported by Remote Copy is five minutes. Because of
the overhead involved in creating and deleting snapshots when starting and stopping a
resynchronization, the period you select should be long enough to allow the previous
resynchronization to complete. If a resynchronization is still taking place before the next
scheduled resynchronization, the new resynchronization starts briefly after the previous
resynchronization has completed. Future resynchronizations use the new schedule, starting
one period after the delayed resynchronization took place.
CAUTION: The resynchronization period should be set to allow sufficient time for
the group to complete synchronizing. If too little time is specified, it is possible
that the group will continuously synchronize.