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Failure of Sites A and B
If both sites A and B fail, services must be switched to site C. After sites A and B recover, services are switched back to ensure service continuity. (Assume that the network topology is A-B-C, HyperMetro is deployed between sites A and B, and remote replication is deployed between sites B and C.)
DR Mechanism
When sites A and B fail, take over services at site C as follows:
- Disable protection for the secondary resource at site C (select the remote replication pair/CG between sites B and C and select Disable Protection for Secondary Resource).
- Map the secondary LUNs at site C to the DR host.
- Enable the DR host to take over services.
Restoration
After services have been failed over to the secondary LUNs at site C, remote replication records the differential data for subsequent incremental data recovery, reducing the failback time.
After the faults are rectified, services are failed back as follows:
- Remove the mappings between the production hosts and storage systems at sites A and B.
- On the storage system at site B, check the Local Resource Host Access Status of the HyperMetro pair. If it is Access prohibited, forcibly start the HyperMetro pair. If it is Read-write and Health Status of the HyperMetro pair is Normal, suspend the HyperMetro pair.
- At site C, perform a primary/secondary switchover for the remote replication relationship between sites B and C. After the switchover, the LUNs at site C become primary LUNs.
- At site C, set the secondary resource to read-only (select the remote replication pair/CG and select Enable Protection for Secondary Resource). This prohibits the hosts from writing the LUNs at site B.
- At site C, synchronize the remote replication pair/CG.
- Stop services at site C.
- Remove the mapping between the host and storage system at site C.
- At site C, synchronize the remote replication pair/CG.
- After the synchronization is complete, split the remote replication pair/CG at site C and set the secondary resource to readable and writable (select the remote replication pair/CG and select Disable Protection for Secondary Resource).
- At site B, map the LUNs to the production hosts.
- Enable the production hosts to take over services.
- At site B, start HyperMetro pair synchronization.
- At site A, map the LUNs to the production hosts.
- After HyperMetro pair synchronization is complete, perform a primary/secondary switchover for the remote replication relationship between sites B and C. After the switchover, the LUNs at site B become primary LUNs. Then, set the secondary resource to read-only and synchronize the remote replication relationship between sites B and C.
