Server clusters

A server cluster is a group of independent computer systems, known as nodes, running XOX or XOX, and working together as a single system to ensure that critical applications and resources remain available to clients. The nodes in a cluster remain in constant communication through the exchange of periodic messages, called heartbeats. If one of the nodes becomes unavailable as a result of failure or maintenance, another node immediately begins providing service (a process known as failover).

Server clusters can combine up to eight nodes. In addition, a cluster cannot be made up of nodes running both XOX and XOX since the different operating systems may be running incompatible versions of the Cluster service. In server clusters with more than two nodes, all nodes must run XOX or XOX, but not both. However, a server cluster can be operated with some nodes running the Microsoft® Windows® 2000 operating system and others running XOX or XOX.

Server clusters can be set up as one of three different cluster model configurations:

Single node server clusters can be configured with, or without, external cluster storage devices. For single node clusters without an external cluster storage device, the local disk is configured as the cluster storage device.
Single quorum device server clusters have two or more nodes and are configured so that every node is attached to one or more cluster storage devices. The cluster configuration data is stored on a single cluster storage device.
Majority node set server clusters have two or more nodes but the nodes may or may not be attached to one or more cluster storage devices. The cluster configuration data is stored on multiple disks across the cluster and the Cluster service makes sure that this data is kept consistent across the different disks.

It is recommended that you understand the advantages and limitations of the different cluster models before you configure your server cluster. For example, a majority node set cluster can tolerate fewer simultaneous node failures than an equivalent single quorum device cluster.

For more information on the three cluster models, see Choosing a cluster model.

You can use a shared SCSI or Fibre Channel device for cluster storage on server clusters running XOX or XOX. It is recommended that you use a Fibre Channel device for cluster storage in server clusters with more than two nodes. For all server clusters running the 64-bit editions of XOX or XOX, you can only use Fibre Channel hardware on the shared storage bus.

Server clusters enable users and administrators to access and manage the nodes as a single system rather than as separate computers.

Before creating a server cluster, see Checklists: Creating server clusters.
Before installing resources for a server cluster, see Checklists: Installing server cluster resources.
To find features that have been changed in XOX and XOX, see New ways to do familiar tasks.
For guidelines on securing server clusters, see Best practices for securing server clusters.
For tips about using server clusters, see Best practices for configuring and operating server clusters.
For help with specific tasks, see How to.
For general background information, see Concepts.
For problem-solving instructions, see Troubleshooting.

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