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Cap. 11. Utilization and Placement Strategy


11.1. Background
11.2. Utilization attributes
11.3. Placement Strategy
11.4. Allocation Details
11.4.1. Which node is preferred to be chosen to get consumed first on allocating resources?
11.4.2. Which resource is preferred to be chosen to get assigned first?
11.5. Limitations
11.6. Strategies for Dealing with the Limitations

11.1. Background

Pacemaker decides where to place a resource according to the resource allocation scores on every node. The resource will be allocated to the node where the resource has the highest score. If the resource allocation scores on all the nodes are equal, by the default placement strategy, Pacemaker will choose a node with the least number of allocated resources for balancing the load. If the number of resources on each node is equal, the first eligible node listed in cib will be chosen to run the resource.
Though resources are different. They may consume different amounts of the capacities of the nodes. Actually, we cannot ideally balance the load just according to the number of resources allocated to a node. Besides, if resources are placed such that their combined requirements exceed the provided capacity, they may fail to start completely or run with degraded performance.
To take these into account, Pacemaker allows you to specify the following configurations:
  1. The capacity a certain node provides.
  2. The capacity a certain resource requires.
  3. An overall strategy for placement of resources.