On a node in a Windows Server 2008 failover cluster, you add a new disk. This new disk contains some highly available resources. You move the disk resource to another node, and then, on this other node, you extend a volume on the disk. In this scenario, the volume GUID for the disk changes, and then the applications that use the disk cannot access the shared volume data. For e.g., if you use Microsoft System Center Virtual Machine Manager (SCVMM) to manage the virtual machines on the disk, you receive the following error message (see screenshot). Cause: This issue occurs because the cluster volume GUID is updated when a disk resource is moved to another node, and then, on this other node, a volume on the disk is extended. Microsoft issued a hotfix to resolve the issue where GUIDs change. It’s post-SP2 fix KB970529.