4.8. Configuring a Failover Domain
- 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.
NoteThe failback characteristic is applicable only if ordered failover is configured.
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.
4.8.1. Adding a Failover Domain
- From the cluster-specific page, you can configure failover domains for that cluster by clicking onalong the top of the cluster display. This displays the failover domains that have been configured for this cluster.
- Click Add Failover Domain to Cluster dialog box, as shown in Figure 4.8, “luci failover domain configuration dialog box”.. Clicking causes the display of the
Figure 4.8. luci failover domain configuration dialog box
- In the Add Failover Domain to Cluster dialog box, specify a failover domain name at the text box.
NoteThe name should be descriptive enough to distinguish its purpose relative to other names used in your cluster.
- To enable setting failover priority of the members in the failover domain, click thecheck box. With checked, you can set the priority value, , for each node selected as members of the failover domain.
NoteThe priority value is applicable only if ordered failover is configured.
- To restrict failover to members in this failover domain, click thecheck box. With checked, services assigned to this failover domain fail over only to nodes in this failover domain.
- To specify that a node does not fail back in this failover domain, click thecheck box. With checked, if a service fails over from a preferred node, the service does not fail back to the original node once it has recovered.
- Configure members for this failover domain. Click thecheck box for each node that is to be a member of the failover domain. If is checked, set the priority in the text box for each member of the failover domain.
- Click Failover Domains page with the newly-created failover domain displayed. A message indicates that the new domain is being created. Refresh the page for an updated status.. This displays the