Multiple Node Server Clusters

Server Clusters offer the same type of availability services as NLB clusters, but use a different model. Whereas in NLB clusters servers do not have to be identical, it is the purpose of the Server Cluster to make identical servers redundant by allowing immediate failover of hosted applications or services. As illustrated in Figure 9-2, Windows Server 2003 supports either four-node (with the Enterprise edition) or eight-node clusters (with the Datacenter edition).

Server Clusters can include several configurations. You can design the cluster so that each node will perform different tasks, but will be ready to fail over any of the other nodes' services and applications. Or you can design the cluster so that applications operate at the same time on each of the nodes. For example, you could design a four-node financial database cluster so that the first node managed order entry, the second order processing, the third payment services, and the fourth the other accounting activities. To do so, your application must be fully cluster aware—completely compliant with all of the Microsoft Cluster Services (MSCS) features. Not all applications or even WS03 services are fully cluster aware.

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