|System Settings, Defaults, Clusters, and Active Directory Authentication / Configuring and Managing Clusters|
You can remove a standby server from a cluster at any time. You cannot remove the active server unless you first fail over control to another node.
When you remove a standby server from a cluster, it becomes active as a standalone server. This standalone server does not interfere with the cluster, because it has a different IP address than the active server, and the active server knows that it is no longer a cluster member if a failover occurs.
To remove a server from the cluster: