3.3. Resource Trees - Basics / Definitions

The following illustrates the structure of a resource tree, with a correpsonding list that defines each area.
    <service name="foo" ...>
        <fs name="myfs" ...>
            <script name="script_child"/>
        </fs>
        <ip address="10.1.1.2" .../>
    </service>
  • Resource trees are XML representations of resources, their attributes, parent/child and sibling relationships. The root of a resource tree is almost always a special type of resource called a service. Resource tree, resource group, and service are usually used interchangeably on this wiki. From rgmanager's perspective, a resource tree is an atomic unit. All components of a resource tree are started on the same cluster node.
  • fs:myfs and ip:10.1.1.2 are siblings
  • fs:myfs is the parent of script:script_child
  • script:script_child is the child of fs:myfs

3.3.1. Parent / Child Relationships, Dependencies, and Start Ordering

The rules for parent/child relationships in the resource tree are fairly simple:
  • Parents are started before children
  • Children must all stop (cleanly) before a parent may be stopped
  • From these two, you could say that a child resource is dependent on its parent resource
  • In order for a resource to be considered in good health, all of its dependent children must also be in good health