Logical Representation of a Windows Cluster

In DPX, you define nodes and node groups. For a Windows cluster, you define physical nodes for the client machines and a single virtual node for the shared resources. All the nodes (physical and virtual) must be members of the same node group. A node group for a cluster must contain all the nodes for that cluster and no other nodes.

The following illustration shows a logical representation for the cluster depicted in the topic above. You define two physical nodes (Node X and Node Y) and one virtual node (BEXClus). The virtual node contains all the shared resources (G: and H:). Logically then, the cluster node group simply contains three nodes: Node X, Node Y, and Clust. Each of the three nodes contains two disks.

All shared resources (for example, files on shared disks, Exchange, SQL Server) are viewed by DPX as local resources of the virtual node.

This concept is illustrated by the following extract from a File Backup window. In this depiction, WIN2003CLUST2 and WIN2003CLUST3 are physical nodes and CLUST is the virtual cluster node. Q:, SQL$SQL2K5SRV:, X:, Y:, and Z: are shared resources. W2K3CLUST is the node group.

With this structure, DPX ensures that backups of the shared resources are performed through the virtual node and backups of local resources are performed through the physical nodes.

For File backups, if a failover occurs during backup of a shared resource, the backup task first fails, then DPX retries the task through an available node. Because the resource runs on an available node, the task completes successfully.

For Block backups, failover during backup results in an unsuccessful backup job. The user must rerun the job or wait until the next scheduled instance of that job.