Moving Production To Site B After Unplanned Outages (Failover) - IBM DS8000 User Manual

Moving production to Site B after unplanned outages (failover)

For this scenario, assume that an unexpected failure occurs at Site A. The failure at
Site A causes the volumes to be suspended or causes a mix of suspended and full
duplex volume pairs because the input might have been written to those volumes
when the failure occurred.
In a disaster recovery environment, when two storage units are set up in two
geographically distinct locations, the storage unit at the production or local site is
referred to as Site A, and the storage unit at the remote or recovery site is referred
to as Site B.
The failover operation is performed on the storage unit that will become the
primary. Production is moved to Site B during this outage, which makes the target
volumes at Site B convert to source volumes. The volumes are designated as in a
suspended state. Your original source volumes at Site A remain in the state that
they were in at the time of the site switch. When Site A is available again,
application I/O is switched back from Site B to Site A.
The following steps summarize the actions you must take to move production to
Site B as the result of an unplanned outage and then return production to Site A
after it recovers.
1. Perform a failover recovery operation to Site B. After the failover operation has
2. Mount your target volumes on your server at Site B.
3. Start your applications on your server at Site B.
4. After Site A recovers, proceed with the following steps, which are the first steps
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processed successfully, the volumes at Site B transition from target to source
volumes.
toward the recovery of the volumes at Site A.
a. Create paths between LSSs at Site B to Site A to allow the volumes at Site A
to be synchronized with the Site B volumes.
b. Delete any remote mirror and copy volume relationships that still exist from
the source volumes.
c. Wait until the volumes are in full duplex state, and then schedule a time to
perform a failback recovery operation using the volumes at Site A. This
process resynchronizes the volumes at Site A with the volumes at Site B.
Note: Failback recovery operations are usually used after a failover
recovery has been performed to restart mirroring either in the reverse
direction (remote site to local site) or in the original direction (local
site to remote site).