A rolling upgrade allows you to upgrade cluster nodes that are running Windows NT 4.0 Enterprise Edition to Windows 2000 Advanced Server. The upgrade is performed in such a way that services and resources remain available to users even throughout the upgrade process. Nodes are upgraded one at a time, ensuring that one cluster node is always available. The only downtime experienced is the time to takes to move resources from one cluster member to another.

Performing a rolling upgrade also minimized risk - if the upgrade on one node fails, the other node is still available. The upgrade can be performed at any time because the resources are still available to clients on the second cluster member.

Not all resources will support a rolling upgrade. However, a rolling upgrade can still be performed, but those specific resources will need to be taken offline during the upgrade process.

If you are performing a rolling upgrade, be sure to plan ahead. Windows 2000 Advanced Server does not have an uninstall option. If you need to return to your previous version of Windows, you will need to reinstall the operating system along with all the applications.

In order to perform a rolling upgrade, your cluster nodes must first meet the preliminary requirements. Each cluster node must be running the following software:

• Windows NT Server 4.0 Enterprise Edition

• SP4 or later
• Microsoft Cluster Service
• IIS 4.0 (if the cluster has an IIS resource)

When you are preparing your computers for the upgrade, make sure that the service pack is reapplied after installing IIS 4.0 and Microsoft Cluster Service.

During the upgrade process, one node in the cluster is paused and its resources are moved to the second node in the cluster. The upgrade to Windows 2000 Advanced Server can then be performed on the first cluster node while the second node continues to handle client requests (the upgrade process can be initiated by running Winnt32.exe from the CD-ROM or from a network share).

The setup program will not only upgrade the operating system but also will detect the previous version and automatically upgrade to clustering for Windows 2000 Advanced Server.

Once the upgrade process has been completed and tested on the first cluster node, the node can be resumed. The upgrade process can then be performed on the second cluster node while the newly upgraded cluster member responds to client requests.

Tags: upgrade, diana huggins, cluster node, rolling upgrade, advanced server