For a rolling upgrade to be successful, two requirements must be met. The first, which was discussed in the first installment of this article, is that the cluster nodes must be running the necessary software.

The second requirement is that all the resources managed by the cluster must support a rolling upgrade. If there are some resources that do not support this upgrade method, you can take those resources offline or perform a clean installation of Cluster Service and reconfigure the cluster nodes after the installation is complete.

At some point during the upgrade process, the cluster members will be running in mixed mode: one will be running Windows NT 4.0 Enterprise Editions and the other will be running Windows 2000 Advanced Server. It is important to remember that if you add a resource to the cluster while it is running in mixed mode, it may not be supported by both operating systems. If, while the cluster is running in mixed mode, you add a resource that is supported by Windows 2000 Advanced Server but not by Windows NT 4.0 Enterprise Edition, the resource will not fail over to the node running the down-level operating system.

Any of the following resource types added while the cluster in running in mixed mode will not fail over to the node running the down-level operating system:

• WINS resource

• DHCP resource
• DFS root file share

Although not a requirement for Cluster Service, it is recommended that fault-tolerant RAID be implemented on the local disks and the shared disk to ensure high availability of the data. Hardware-level RAID is the only option for the shared disk because software RAID can not be used by Cluster Service.

Whether software-level RAID on the local disks will be implemented under Windows 2000 Advanced Server needs to be considered before performing a rolling upgrade. In order to implement software-level RAID under Windows 2000 Advanced Server, the disk must be a dynamic disk. Once the upgrade has been completed, the disk has to be converted from basic to dynamic in order to implement RAID 1 or RAID 5. If you want the local disks to remain as basic disks, software-level RAID must be in-place before you perform the upgrade. Windows 2000 can only implement software-level RAID on a dynamic disk unless the RAID was configured before the upgrade. Otherwise, the local disks will need to be converted to dynamic.

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