Cluster

What is Cluster (in computer networking)?

A configuration of two nodes in Microsoft Cluster Server (MSCS). When network clients try to access shared resources or applications on clusters, the cluster appears to the clients as a single server.

MSCS is included with Microsoft Windows NT Server, Enterprise Edition. (For a similar feature in Windows 2000, see Windows Clustering.)

How Cluster work

Each node in a cluster is a completely independent computer system that must be running Windows NT Server, Enterprise Edition. These nodes are connected by a shared storage bus such as an external Small Computer System Interface (SCSI) disk subsystem.

Network resources such as applications and shared information can be hosted on only one node at a time, but MSCS supports failover, which allows the resource to be shifted to the other node if one of the nodes in a cluster fails. Failover is controlled by the Cluster service, which runs on both nodes.

Some of the different models for configuring a cluster on MSCS include

• High availability with static load balancing, in which both nodes make their resources available to network users as virtual servers and either node can take on the work of the other should failover be initiated. This configuration is typically used for file-sharing or print-sharing purposes.
• High availability with hot-spare support, in which the primary node is active and provides resources to network users, while the secondary node is inactive and is used only as a dedicated backup node. This configuration is typically used for mission-critical Web services.