Dell Storage Manager 2020 R1 Administrator's Guide

Phase 3—Restore Cluster A and fail back from Cluster B to Cluster A

After you have fixed the reason that caused Cluster A to fail, fail back over to Cluster A.

1. Fix the reason that caused Cluster A to fail and if required reinstall FluidFS.
2. Rebuild the FluidFS cluster:
   • IP address-based failovers: Use the settings for Cluster A that you recorded earlier, but change the IP addresses for Cluster A to match the IP addresses originally used by Cluster B.
   • DNS-based failovers: Use the settings for Cluster A that you recorded earlier.
3. From Cluster B, set up a replication partnership between Cluster B and Cluster A.
4. Configure replication for all the promoted recovery volumes in Cluster B, and specify that they replicate back to the original source volumes in Cluster A.

   The replication policy must be a one-to-one match on a volume basis, for example:

   Source volume B1 (Cluster B) to target volume A1 (Cluster A)

   Source volume B2 (Cluster B) to target volume A2 (Cluster A)

   Source volume Bn (Cluster B) to target volume An (Cluster A)

5. Manually perform replication on the promoted recovery volumes in Cluster B (B1, B2, .., Bn). Proceed to the next step when replication completes.

   If the replication fails, fix the problems encountered and restart the replication process. Ensure that all the NAS volumes are successfully replicated to Cluster A.

6. From Cluster A, promote the original source volumes (A1, A2, .., An).
7. From Cluster B, delete replication for the promoted recovery volumes (B1, B2, .., Bn) and apply the source volume configuration from Cluster B to Cluster A. Repeat this procedure to delete all the replication policies and bring all target volumes in Cluster A to standalone NAS volumes.
8. From Cluster A, restore the users and groups configuration from Cluster B. This restores the Cluster A users and groups configuration to Cluster B settings.
   NOTE:If the system configuration restore fails, manually set the system back to the original settings (use the settings for Cluster A that you recorded earlier).
9. Start using Cluster A to serve client requests.
   1. Choose one of the following options:
      • IP address-based failovers: Change the IP addresses for Cluster A to match the IP addresses originally used by Cluster A and change the IP addresses for Cluster B to match the IP addresses originally used by Cluster B. Existing client connections might break and might need to be re-established.
      • DNS-based failovers: Point the DNS names from your DNS server to Cluster A instead of Cluster B.

        Ensure that the DNS server on Cluster A is the same as the DNS server or in the same DNS farm as the DNS server of Cluster B. Existing client connections might break and might need to be re-established. You must unmount and re-mount the NFS Exports on the client.

   2. (Single NAS volume failovers) Manually update the DNS entry for the NAS volume that was failed over. This redirects clients that are accessing this volume from Cluster B to Cluster A, while other clients keep accessing other volumes using the same DNS name. Client systems might need to refresh their DNS cache.
   3. (Single NAS volume failovers) To force SMB and NFS clients to Cluster A, you must delete the SMB shares and NFS exports on Cluster B. This forces the SMB and NFS clients to reconnect, at such time they are connected to Cluster A. After restoring the source volume’s configuration on Cluster A, all of the SMB shares and NFS exports will be present on the target volume (on Cluster A), so no SMB share/NFS export configuration information is lost.

      The failed over volume can now be accessed using the exact same DNS name and SMB share/NFS export name as it was when hosted on Cluster B, except now it is hosted on Cluster A.

   4. Join Cluster A to the AD server or LDAP/NIS.
   5. From Cluster A, configure replication between the original source volumes (A1, A2,.. , An) and the original target volumes (B1, B2,.. , Bn) to prepare for the next disaster recovery.