What the IT Manager Should Know

A server cluster is a set of independent servers (referred to as nodes) and connected storage devices that are managed together. They present a single view of the server to users, applications, and the network. Windows 2000 Advanced Server supports two-node clusters, and Datacenter Server supports four-node clusters.

Figure 1: Cluster service lets you connect two servers to help ensure site availability.

Clustered servers are physically connected by cables and programmatically connected by cluster software. Clusters use an algorithm to detect a failure, and failover policies to determine how to handle the work from the failed server. These policies also specify how a server is to be restored to the cluster when it becomes available again.

The servers do not have to be the same size or have the same configuration. For example, you can run exactly the same applications on both servers and have one of them idle, ready to pick up all operations and sustain high performance. Or you can have both servers online at the same time, with a variety of options for what applications are running on each server.

This flexible model allows you to configure Cluster service to provide the best value and protection for your particular circumstances. To simplify configuration, Windows 2000 Advanced Server includes Cluster Administrator. Using this facility, you can configure and manage the cluster from a central location, even from a remote location. After you’ve established a cluster, you can move workloads around between the servers while performing maintenance and testing without interrupting users. This ability to move workloads back and forth also makes it possible to do rolling software upgrades without interrupting users.

Note: While Cluster service is used to ensure the availability of your back-end servers, a related clustering technology called Network Load Balancing (NLB) lets you increase the availability of the network servers used to handle incoming user requests. To learn more about NLB, see the Solution Spotlight "Keep Applications Responsive with Network Load Balancing."

Conclusion

A basic requirement for critical business applications is that they are always available for use. With the Cluster service in Windows 2000 Advanced Server, you can be assured that in spite of failure or required maintenance, your employees and customers will be able to access the applications they need, when they need them.

For more information go to www.microsoft.com  and search on clustering