I used the Microsoft article "How to install Exchange Server 2003 Service Pack 1 in a clustered Exchange environment" at http://www.support.microsoft.com/?kbid=867624 to guide me through applying Exchange Server 2003 Service Pack 1 (SP1) on the cluster nodes. Here are the basic steps I followed to apply the service pack:

  1. Apply the service pack to the passive node first and reboot the server.
  2. Take the Exchange services offline by using Cluster Administrator and move the virtual server to the node just updated.
  3. Right-click the group that contains the Exchange virtual server and choose Upgrade Exchange Virtual Server.
  4. Install the service pack on the other cluster node to complete the upgrade.