Failover

Failover occurs when a server in a cluster automatically switches over to one or more backup servers in the event of a system failure.

Contrast this with a switchover, which happens when you manually switch access from one server to another. A switchover and a failover function identically once they have been triggered. The only difference is how the event is triggered.

When a failover occurs, access is switched from the cluster node currently acting as the primary node in the recovery domain of the cluster resource group to the cluster node designated as the first backup. See recovery domain for information about how the switchover order is determined.

When multiple cluster resource groups (CRGs) are involved in a failover action, the system processes the device CRGs (switchable devices) first, the data CRGs (switchable data groups) second, and the application CRGs (switchable applications) last.

The failover message queue receives messages regarding failover activity. You can use it to control the failover processing of a cluster resource group.

• Example: Failure
  Usually, a failover results from a node failure, but there are other reasons that can also generate a failover.