24.2. Pacemaker resource allocation

Pacemaker allocates resources according to node preference, node capacity, and resource allocation preference.

Pacemaker determines which node is preferred when allocating resources according to the following strategy.

The node with the highest node weight gets consumed first. Node weight is a score maintained by the cluster to represent node health.
If multiple nodes have the same node weight:
- If the placement-strategy cluster property is default or utilization:
  - The node that has the least number of allocated resources gets consumed first.
  - If the numbers of allocated resources are equal, the first eligible node listed in the CIB gets consumed first.
- If the placement-strategy cluster property is balanced:
  - The node that has the most free capacity gets consumed first.
  - If the free capacities of the nodes are equal, the node that has the least number of allocated resources gets consumed first.
  - If the free capacities of the nodes are equal and the number of allocated resources is equal, the first eligible node listed in the CIB gets consumed first.
- If the placement-strategy cluster property is minimal, the first eligible node listed in the CIB gets consumed first.

Pacemaker determines which node has the most free capacity according to the following strategy.

If only one type of utilization attribute has been defined, free capacity is a simple numeric comparison.
If multiple types of utilization attributes have been defined, then the node that is numerically highest in the most attribute types has the most free capacity. For example:
- If NodeA has more free CPUs, and NodeB has more free memory, then their free capacities are equal.
- If NodeA has more free CPUs, while NodeB has more free memory and storage, then NodeB has more free capacity.

Pacemaker determines which resource is allocated first according to the following strategy.

The resource that has the highest priority gets allocated first. You can set a resource’s priority when you create the resource.
If the priorities of the resources are equal, the resource that has the highest score on the node where it is running gets allocated first, to prevent resource shuffling.
If the resource scores on the nodes where the resources are running are equal or the resources are not running, the resource that has the highest score on the preferred node gets allocated first. If the resource scores on the preferred node are equal in this case, the first runnable resource listed in the CIB gets allocated first.