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200 Configuration: Premium Feature— Remote Replication
Automatically Resynchronizing Virtual Disks
When automatic resynchronization is selected, the RAID controller module
owning the primary virtual disk automatically starts resynchronizing the data
on the remote replication pair immediately after communication is restored.
NOTE: When choosing automatic resynchronization, a possible loss of data can
occur if a resynchronization is interrupted in progress. Since another
resynchronization begins automatically after communication is restored between
the primary virtual disk and the remote virtual disk, data integrity could be affected.
With automatic resynchronization set, you cannot add a secondary virtual
disk to a write consistency group. Therefore, write consistency during the
resynchronization process is not preserved. The write order is not consistent
until the entire group achieves Optimal status.
Manually Resynchronizing Virtual Disks
When manual resynchronization is selected, you must manually
resynchronize and resume the data transfer on a remote replication after
communication is restored between the primary and remote virtual disks.
Manual resynchronization is the recommended setting for all remote
replications for these reasons:
• You determine when resynchronization starts, which allows you to better
manage and/or mitigate impact on I/O performance.
• In a disaster recovery situation, manual resynchronization offers the best
chance of retrieving valid data.
• When the secondary virtual disk is in a write consistency group, manual
resynchronization preserves the write order.
book.book Page 200 Wednesday, June 8, 2011 5:01 PM