Backup Group Leader Array

The backup group leader array helps you maintain service and ensure high availability if the group leader array becomes unresponsive or there is a planned outage that affects the group leader. The backup group leader stores replicated configuration data. It keeps this data in sync with the group leader data.

Each group can have one backup group leader.

A backup group leader enables you to:
  • Migrate the functions of the group leader array to the backup group leader array.

    When you have a backup group leader set up, you can migrate the current group leader to the backup group leader. Doing this lets you seamlessly accommodate any scheduled issues that require you to halt or remove the group leader array.

    You initiate a migration from the group leader array using either the GUI or the CLI:

    • GUI method: Attempt to shutdown the group leader array from the GUI. The system displays a message stating that the array is performing management services and asking if you want to migrate the group leader to the backup group leader before halting the array. If you select this option, the array OS automatically performs the migration.
    • CLI method: From the group leader array, run the following commands:
      • group --check_migrate to confirm that it is OK to perform the migration. You can perform a migration operation only if the backup group leader array is in synch with the group leader array.
      • group --migrate to migrate the group leader functions to the backup group leader.

    After your backup group leader becomes the group leader, you can specify a different secondary management IP address to designate another backup group leader.

  • Set up Automatic Switchover (ASO) to enable the backup group leader to automatically take over the group leader role if it detects that the group leader is unresponsive. ASO automatically creates a backup group leader.

    If the backup group leader can no longer get a response from the group leader, ASO promotes the backup group leader array to the group leader array.

    To use ASO, you must either install and configure a Witness daemon on a Linux server, or run the daemon in a separate VM. For information about ASO, see Automatic Switchover (ASO).

  • Perform a manual takeover using the OS CLI group --takeover command to promote the backup group leader array to group leader. You must run this command from the backup group leader. You cannot perform this operation if you have ASO enabled and a witness installed.
    NOTE: You should take down your cluster before you perform a manual takeover. This enables you to have a predictable recovery and avoid having host interactions while changes are being made on the array side. If Peer Persistence (synchronous replication and ASO) is not configured when the group leader goes down, the host generally loses access to all Group Scoped Target (GST) LUNs.
    Before you can perform a takeover, the following two conditions must be true:
    • The OS CLI group --check_takeover command says it is OK to perform a takeover.
    • The group leader array is unresponsive and cannot be reached by the backup group leader array.