Priority attribute

You use the Priority persistent attribute to specify the relative priority of this resource group in relationship to other resource groups.

The Priority attribute is used to resolve conflicts when resource groups are being started that have conflicting managed relationships (described in Managed relationships) to other started or online resources. These conflicts may be between the resource group or a managed resource contained in that group and any other started or running resource.

For resource groups that have the same actual priority, the number of non-mandatory members determines the order. The group with the lowest number of non-mandatory members is sacrificed first. If the groups have the same actual priority and the same number of non-mandatory members, the algorithm decides incidentally which group will be removed from the binding problem. This relaxes the overdetermined constraint satisfaction problem. This removal is called sacrificing since it causes the groups and their members to stop (stay offline), regardless of their desired state.

For instance, you have a cluster with only one node online, and two resource groups with an AntiCollocated relationship against each other. This means that the resource groups must never be started on the same node at a time. System Automation for Multiplatforms now uses the value of the Priority attribute of the resource groups to find out which of the resource groups should be online, and which cannot be online because of the conflicting AntiCollocated relationship.

If a lower priority active resource group prevents the activation of a higher priority resource group because of conflicting relationships, the lower priority resource group is stopped in order to allow the activation of the resource group with higher priority to proceed.

If resource groups are nested, the outer resource group must have a higher or equal priority than any of the inner resource groups.

The default value of the Priority attribute is zero, which is the lowest value. The maximum value is 200.

The actual priority of a resource group is computed from the value of the priority attribute and an adjustment value which is determined by the current observed state of the group (see AutomationDetails attribute) . The adjustment value for groups that are online is +10, to make sacrificing started resources harder, and -10 for groups that are failed offline. The actual priority value can assume values from -10 to +210. For more information on the meaning of the priority, see Assigning node location.