Reasons for Using Server Clusters

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Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

This section discusses specific clustering features that help the Operations and Technology Group (OTG) achieve their objectives.

A server cluster is a collection of servers known as nodes that together provide a single, highly available system for hosting applications. Multiple nodes in a cluster remain in constant communication. A clusters resources and applications are organized into functional units called resource groups. Each resource group is assigned to a node and can only be owned by a single node at any point in time.

There are three primary benefits to using server clusters. Server clusters are highly available, scalable, and easy to manage.

  • Highly available: Server clusters provide a highly available system for deploying applications. You can use server clusters to protect against failures of hardware, operating systems, device drivers, or applications. If one of the nodes in a cluster is unavailable as a result of failure or maintenance, another node immediately begins providing service (a process known as failover). Server clusters also allow you to upgrade the operating system and application software with minimal downtime.

  • Scalable: Server clusters provide scalability for important resources and applications. When the overall load of a cluster exceeds its capabilities, you can incrementally add additional nodes to the cluster. In Windows Server 2003, server clusters can include up to eight nodes.

  • Easy to manage: In a server cluster, you can quickly inspect the status of all cluster resources and move workloads around onto different nodes. Because you can move processing to alternate nodes, you can perform rolling upgrades on the servers. In a rolling upgrade, a server cluster continues to provide service while software is being upgraded on each node until all nodes have been upgraded.

Microsoft has used these cluster features to help achieve its technical and business objectives. These objectives are described in the following section.