Server clusters overview

A server cluster is a group of independent computer systems, known as nodes, working together as a single system to ensure that critical applications and resources remain available to clients. These nodes must be running XOX or XOX. Clustering allows users and administrators to access and manage the nodes as a single system rather than as separate computers. For more information about nodes, see Nodes.

A server cluster can consist of up to eight nodes and may be configured in one of three ways: as a single node server cluster, as a single quorum device server cluster, or as a majority node set server cluster. For more information about these three server cluster models, see Choosing a cluster model.

Every node may be attached to one or more cluster storage devices. You can use a shared SCSI or Fibre Channel device for cluster storage on server clusters running XOX or XOX. For server clusters with more than two nodes, it is recommended that you use Fibre Channel hardware on the shared storage bus. For 64-bit editions of XOX or XOX, cluster disks on a shared bus must use Fibre Channel hardware.

A server cluster runs several pieces of software that fall into two categories: the software that makes the cluster run (clustering software) and the software that you use to administer the cluster (administrative software). By default, all clustering and administration software files are automatically installed on your computer when you install any operating system in the Microsoft® Windows® Server 2003 family of products.

Important

• Only computers running XOX or XOX can be cluster nodes.

Clustering software

The clustering software enables the nodes of a cluster to exchange specific messages that trigger the transfer of resource operations at the appropriate times. There are two main pieces of clustering software: the Resource Monitor and the Cluster service. The Resource Monitor facilitates communication between the Cluster service and application resources. The Cluster service runs on each node in the cluster and controls cluster activity, communication between cluster nodes, and failure operations. When a node or application in the cluster fails, the Cluster service responds by restarting the failed application or dispersing the work from the failed system to the remaining nodes in the cluster. For more information about this process, see Failover and failback.

For more detailed information on the components of the clustering software, see the Microsoft Windows Server 2003 Resource Kit.

Administrative software

Administrators use cluster management applications to configure, control, and monitor clusters. The Windows Server 2003 family provides Cluster Administrator for this purpose. Any computer running Microsoft Windows NT® version 4.0 Service Pack 3 or later, regardless of whether it is a cluster node, can install Cluster Administrator. By default, a copy of Cluster Administrator is automatically installed on your computer when you install XOX; XOX; or XOX. For information on remote administration, see Installing Cluster Administrator on a remote computer.

You can also create, configure, and administer clusters using the cluster command. For more information, see Administering server clusters. You can use or create custom administration tools developed using the Cluster automation interfaces. For more information on the Cluster automation interfaces, see the Microsoft Platform Software Development Kit (SDK), available separately.

Administrators organize cluster resources into functional units, called groups, and assign these groups to individual nodes. If a node fails, the Cluster service transfers the groups that were being hosted by the node to other nodes in the cluster. This transfer process is called failover. The reverse process, failback, occurs when the failed node becomes active again, and the groups that were failed over to other nodes are transferred back to the original node. For more information about resources, see Server cluster resources. For more information about groups, see Groups.