Installation guide

Appendix D. HA Resource Behavior
This appendix describes common behavior of HA resources. It is meant to provide ancillary
information that may be helpful in configuring HA services. You can configure the parameters
with Luci, system-config-cluster, or by editing etc/cluster/cluster.conf. For
descriptions of HA resource parameters, refer to Appendix C, HA Resource Parameters. To
understand resource agents in more detail you can view them in /usr/share/cluster of any
cluster node.
Note
To fully comprehend the information in this appendix, you may require detailed
understanding of resource agents and the cluster configuration file,
/etc/cluster/cluster.conf.
A cluster service is a group of cluster resources configured into a coherent entity that provides
specialized services to clients. A cluster service is represented as a resource tree in the cluster
configuration file, /etc/cluster/cluster.conf (in each cluster node). In the cluster
configuration file, each resource tree is an XML representation that specifies each resource, its
attributes, and its relationship among other resources in the resource tree (parent, child, and
sibling relationships).
Note
Because a service consists of resources organized into a hierarchical tree, a
service is sometimes referred to as a resource tree or resource group. Both
phrases are synonymous with cluster service.
At the root of each resource tree is a special type of resource — a service resource. Other types
of resources comprise the rest of a service, determining its characteristics. Configuring a cluster
service consists of creating a service resource, creating subordinate cluster resources, and
organizing them into a coherent entity that conforms to hierarchical restrictions of the service.
This appendix consists of the following sections:
• Section 1, “Parent, Child, and Sibling Relationships Among Resources”
• Section 2, “Sibling Start Ordering and Resource Child Ordering”
• Section 3, “Inheritance, the <resources> Block, and Reusing Resources”
• Section 4, “Failure Recovery and Independent Subtrees”
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