Features and Benefits of HSG80 ACS 8.6P Data Replication Manager

Features and Benefits of HSG80 ACS 8.6P Data Replication Manager 11
Remote Copy Set
A remote copy set is a bound set of two units used for long distance mirroring. Each unit can be a
single JBOD disk, RAID-0 stripeset, RAID 1 mirrorset, or RAID 0+1 Stripe-Mirrorset or RAID
3/5 RAID set. In Figure 4, the LUN Remote Copy Set (RCS1) consists of Unit A and Unit C.
RCS2 consists of Unit B and Unit D.
During replication, the local side of the remote copy set can be made visible to any of the hosts on
the SAN. The target side of the remote copy set is owned by the local or initiator controller and is
unavailable for use by a server. During failover conditions, the target temporarily becomes the
initiator and the initiator becomes the target with replication going in the reverse direction. Again,
only the initiator (or target running in initiator mode) is made visible to the SAN. When available,
business continuance volumes, such as clones or snapshots of the target, are also visible to the
SAN. These target-based snapshots and clones are useful for performing remote backups of the
active databases and use non-RCS LUNs.
Unit B
Unit D
Unit A
Unit C
RCS1
LOCAL
REMOTE
RCS2
Figure 4: Remote copy sets and association sets
Association Set
An association set is the grouping of remote copy sets that can transition to the same state at the
same time. The host uses association sets to keep multiple units consistent with one another. For
example, when one association set member goes failsafe locked inoperative (is no longer
accessible), all association set members go failsafe locked.
With write history logging mini-merge (merge of data in the write history log), write ordering is
maintained for all members within an association set if the option is enabled. As shown in Figure
4, both remote copy sets are included in the one association set and will share the same write
history log disk.