This article describes how to upgrade a Windows NT Server, Enterprise Edition 4.0 server cluster to a Windows Server 2003 Enterprise Server cluster. Because there is a two version difference between Windows NT 4.0 and Windows Server 2003 in the Cluster service, a rolling upgrade is not supported. This means that the server cluster will be unavailable for client access during the upgrade to Windows Server 2003.

How to Upgrade

The following procedure describes the upgrade to Windows Server 2003. Both nodes in the cluster must be running Windows NT 4.0 Service Pack 5 or higher. Verify that the programs that are running on the Windows NT 4.0 cluster will run in Windows Server 2003 after the upgrade. If you are upgrading a server cluster that contains an IIS or MSMQ resource type, see the online help or the "Getting Started" guide. The following instructions assume two nodes that are labeled NodeA and NodeB. NodeA is upgraded first, followed by NodeB. Before you start the upgrade, verify that all users are disconnected because all cluster resources will be unavailable during the upgrade.

1.	Create a complete backup of NodeA, NodeB, and all of the shared disks in the server cluster.
2.	Set the Cluster service on NodeA and NodeB to manual.
3.	Turn off NodeB. NOTE: To prevent possible damage to the shared disk, note that only one node can be turned on during the upgrade to Windows Server 2003 in a Windows NT 4.0 server cluster.
4.	Stop the Cluster service on NodeA.
5.	Upgrade NodeA to Windows Server 2003 by following the instructions on the screen.
6.	Once the upgrade finishes, manually start the Cluster service on NodeA.
7.	Start Cluster Administrator, and then verify that all of the resources are online. IMPORTANT: If all of the resources do not come online as expected, do not continue. You can use one of the following two options if there is a failure and the server cluster needs to be brought back online: • Turn off NodeA (newly upgraded to Windows Server 2003), and then turn on NodeB (still running Windows NT 4.0) bring online all of the resources and run the server cluster with one node. When there is downtime, troubleshoot NodeA and the resources that will not come online. • Restore NodeA from your backup to restore the original Windows NT 4.0 installation.
8.	Set the Cluster service back to automatic on NodeA.
9.	Turn off NodeA.
10.	Upgrade NodeB to Windows Server 2003 by following the instructions on the screen.
11.	Once the upgrade finishes, manually start the Cluster service on NodeB.
12.	Start Cluster Administrator, and then verify that all resources are online.
13.	Set the Cluster service back to automatic on NodeB.
14.	Turn on NodeA and it will automatically join the cluster that NodeB is hosting.