Typical Cluster Configuration

This illustration shows a logical diagram of a Windows Server 2003 cluster composed of three physical servers (or “nodes”) that is being used to host two “virtual” servers. Server Nodes 1 and 2 host “Virtual Server A,” while Nodes 2 and 3 host “Virtual Server B.” Each virtual server provides one or more services (such as file, print, SQL Server, Exchange, or other cluster-enabled applications) to client computers (which could be other servers or users’ workstations). Nodes 1, 2, and 3 each have connections to the corporate data network and to a separate interconnection network (labeled as “Cluster Interconnect” in the diagram) that allows them to monitor the health of the other servers. In this example, Node 2 is dedicated to the “passive” role and is available to take over for either of the “active” Nodes, 1 and 3.

All three nodes also have SAN adapters (either Fibre Channel or iSCSI over Gigabit Ethernet) connecting them to a SAN storage array. Each node has no local disk storage but boots instead from its own dedicated volume on the SAN. (This Windows Server 2003 feature requires support from the SAN vendor.) Nodes 1 and 2 (Virtual Server A) also have access to a common data volume, but only Node 1 can access it until a failover occurs. Similarly, Nodes 2 and 3 (Virtual Server B) have access to a different common data volume, but only Node 3 can access it until a failover occurs.