D.1. Parent, Child, And Sibling Relationships Among Resources; D.2. Sibling Start Ordering And Resource Child Ordering - Red Hat ENTERPRISE LINUX 5 - ADMINISTRATION Manual

Appendix D. HA Resource Behavior
D.1. Parent, Child, and Sibling Relationships Among
Resources
A cluster service is an integrated entity that runs under the control of rgmanager. All resources in a
service run on the same node. From the perspective of rgmanager, a cluster service is one entity that
can be started, stopped, or relocated. Within a cluster service, however, the hierarchy of the resources
determines the order in which each resource is started and stopped.The hierarchical levels consist of
parent, child, and sibling.
Example D.1, "Resource Hierarchy of Service foo"
the example, the relationships among the resources are as follows:
• fs:myfs (<fs name="myfs" ...>) and ip:10.1.1.2 (<ip address="10.1.1.2 .../>) are siblings.
• fs:myfs (<fs name="myfs" ...>) is the parent of script:script_child (<script
name="script_child"/>).
• script:script_child (<script name="script_child"/>) is the child of fs:myfs (<fs
name="myfs" ...>).
<service name="foo" ...>
<fs name="myfs" ...>
<script name="script_child"/>
</fs>
<ip address="10.1.1.2" .../>
</service>
Example D.1. Resource Hierarchy of Service foo
The following rules apply to parent/child relationships in a resource tree:
• Parents are started before children.
• Children must all stop cleanly before a parent may be stopped.
• For a resource to be considered in good health, all its children must be in good health.

D.2. Sibling Start Ordering and Resource Child Ordering

The Service resource determines the start order and the stop order of a child resource according to
whether it designates a child-type attribute for a child resource as follows:
• Designates child-type attribute (typed child resource) — If the Service resource designates a child-
type attribute for a child resource, the child resource is typed. The child-type attribute explicitly
determines the start and the stop order of the child resource.
• Does not designate child-type attribute (non-typed child resource) — If the Service resource does
not designate a child-type attribute for a child resource, the child resource is non-typed. The Service
resource does not explicitly control the starting order and stopping order of a non-typed child
resource. However, a non-typed child resource is started and stopped according to its order in /
etc/cluster.cluster.conf In addition, non-typed child resources are started after all typed
child resources have started and are stopped before any typed child resources have stopped.
96
shows a sample resource tree of the service foo. In