How to install service packs in a cluster

You can install Windows service packs on Windows Server Failover Cluster nodes using the following procedure. Always install the same service packs or hotfixes to each node. Use this procedure to install the service packs unless otherwise directed by a particular service pack version.

Check the System event log for errors and ensure proper system operation.
Make sure you have a current backup and updated emergency repair disk for each system. In the event of corrupt files, power outage, or incompatibility, it may be necessary to revert back to the state of the system prior to attempting to install the service pack.
Open Cluster Administrator, right-click Node A, and then click Pause Node.
Expand Node A, and then click Active Groups. In the left pane, right-click the groups, and then click Move Group to move all groups to Node B.
Install the service pack on Node A, and then restart the computer.
Check the System event log for errors. If you find any errors, troubleshoot them before continuing this process.
In Cluster Administrator, right-click Node A, and then click Resume Node.
In Cluster Administrator, right-click Node B, and then click Pause Node.
Right-click Node B, and then click Move Group for all groups owned by Node B to move all groups to Node A.
Install the service pack on Node B, and then restart the computer.
Check the system event log for errors. If you find any errors, troubleshoot them before continuing this process.
In Cluster Administrator, right-click Node B, and then click Resume Node.
Right-click each group, click Move Group, and then move the groups back to their preferred owner.