Overview of Manual Failover Steps When the Backup Group Leader is Unreachable

When the group leader cannot reach the backup group leader, it transitions to out of sync.

To confirm that the backup group leader is unavailable, use either the NimbleOS GUI or CLI:
  • The Hardware page in the NimbleOS GUI displays a red asterisk next to the backup group leader when it is unreachable.
  • The CLI command group --info |grep -i <group leader> reports that the backup group leader is unreachable.

Before you begin the manual takeover, make sure there is a common snapshot between the two arrays in the group. The common snapshot simplifies the process of re-enabling synchronous replication.

To perform a manual failover when the backup group leader is not available, you must perform the following high-level steps:

  1. Disassociate the downstream volume from the volume collection and remove synchronous replication, which will allow host connections.

    See Remove Synchronous Replication from the Downstream Partner.

  2. Bring the downstream volume online as a non-synchronous replication volume. When you disassociate the downstream volume and bring it online this way, the following happens:
    1. Existing ACLs from the upstream volume are cloned to the downstream volume.
    2. The LUNs on the downstream volume get new numbers.
    3. A new iSCSI serial number is assigned to the downstream volume.
    4. The downstream volume is no longer listed as a downstream volume in the GUI.
  3. (Optional) When the group leader and the backup group leader are in-sync, enable Automatic Switchover (ASO) with the Witness present and set up synchronous replication again.

    See Add Synchronous Replication.

  4. Perform a handover operation.

    See Perform a Handover.