Installation guide

A failover domain is a named subset of cluster nodes that are eligible to run a cluster service in the

event of a node failure. A failover domain can have the following characteristics:

Unrestricted — Allows you to specify that a subset of members are preferred, but that a cluster

service assigned to this domain can run on any available member.

Restricted — Allows you to restrict the members that can run a particular cluster service. If none of

the members in a restricted failover domain are available, the cluster service cannot be started

(either manually or by the cluster software).

Unordered — When a cluster service is assigned to an unordered failover domain, the member on

which the cluster service runs is chosen from the available failover domain members with no

priority ordering.

Ordered — Allows you to specify a preference order among the members of a failover domain. The

member at the top of the list is the most preferred, followed by the second member in the list, and

so on.

Failback — Allows you to specify whether a service in the failover domain should fail back to the

node that it was originally running on before that node failed. Configuring this characteristic is

useful in circumstances where a node repeatedly fails and is part of an ordered failover domain.

In that circumstance, if a node is the preferred node in a failover domain, it is possible for a

service to fail over and fail back repeatedly between the preferred node and another node,

causing severe impact on performance.

Note

The failback characteristic is applicable only if ordered failover is configured.

Note

Changing a failover domain configuration has no effect on currently running services.

Note

Failover domains are not required for operation.

By default, failover domains are unrestricted and unordered.

In a cluster with several members, using a restricted failover domain can minimize the work to set up

the cluster to run a cluster service (such as httpd ) which requires you to set up the configuration

identically on all members that run the cluster service. Instead of setting up the entire cluster to run

the cluster service, you can set up only the members in the restricted failover domain that you

associate with the cluster service.

Red Hat Ent erprise Linux 6 Clust er Administ rat ion