HP 3PAR Operating System Software - Manual (Page 123)

For additional information, see the following:
•
“Working with Volume Groups” (page 110)
•
“Volume Group Modes” (page 120)
Types of Synchronization
Remote copy performs one of two types of synchronization on volume groups:
Functionality Type of Synchronization
HP 3PAR Remote Copy copies the entire primary volume. full synchronization
HP 3PAR Remote Copy copies only the data that has
changed since the previous synchronization. resynchronization
When you create a new volume group, the initial synchronization of data is always a full
synchronization, regardless of mode (asynchronous periodic or synchronous), unless you choose
the -nosync option with the startrcopygroup command or the admitrcopyvv <snapname>
command.
Synchronizations are done individually for each volume.
Depending on the volume group mode, remote copy performs different types of synchronizations
at different times.
Limits on Volumes that Concurrently Synchronize
To limit the impact of remote copy on the performance of the HP 3PAR StoreServ Storage, HP 3PAR
Remote Copy limits the number of virtual volumes that synchronize at the same time to 20 volumes.
This limit:
•
Is not user-configurable.
•
Applies to the initial synchronization.
•
Applies to resynchronizations, regardless of mode (synchronous or asynchronous periodic).
For more information about volume group modes, see “Volume Group Modes” (page 120) .
For example, if remote copy is in the process of resynchronizing an asynchronous periodic mode
volume group that contains 30 virtual volumes, you might notice that some of the first 20 volumes
complete synchronization before some of the last 10 volumes start synchronizing.
To view resynchronizations, monitor the SyncStatus column of the showrcopy command output.
See the HP 3PAR Command Line Reference for complete details on the showrcopy command
an example of showrcopy command output.
To access this document, go to the HP 3PAR StoreServ Storage site and click the Support link for
your product:
www.hp.com/go/3par
To ensure volume group consistency, remote copy maintains all the snapshots for the secondary
asynchronous periodic volume group on the backup system until all of the virtual volumes in that
volume group are synchronized. For more information, see
“Remote-Copy Snapshots” (page 270) .
Asynchronous Periodic Mode Volume Groups
For asynchronous periodic mode volume groups:
1.
The initial synchronization (a full synchronization) creates snapshots on the backup system.
2. Until the primary and secondary volume groups are synchronized again, the primary system
accepts I/O and acknowledges the I/O.
Synchronization 123