Determine the stacking number for a dynamic cluster

We can use profiling to determine the stacking number for the dynamic cluster. The stacking number is the number of cluster instances that are needed to use all the power of a node.

The Allow more than one instance to start on the same node setting in the console enables vertical stacking on the node. When you select this option, you must provide the number of instances to start on the same node. This value is the stacking number.

We can determine the stacking number by profiling of the application. If the dynamic cluster is homogeneous, and all of the nodes for the dynamic cluster have similar power, we need to profile and determine the stacking number on one node only. If the member nodes for the dynamic cluster are heterogeneous and vary in power, profile each node and determine the stacking number for each node.

  1. Start one server instance on the test node.

  2. View CPU utilization and average throughput curves for the node. To view the charts, click Runtime operations > Reports.

  3. Increase the load on the node, with the goal of reaching 90-100% node utilization.

  4. If we cannot reach 90-100% node utilization, add and start another server instance on the test node. Continue adding server instances until the node utilization reaches 90-100%.

  5. The current number of server instances on the test node is the stacking number. Remember this number so that we can configure the stacking number in the console.

  6. If the dynamic cluster has member nodes that are heterogeneous, repeat these steps for each node and record a stacking number for each node.


What to do next

Enable vertical stacking for the cluster. With vertical stacking enabled, the autonomic managers can limit the processor percentage used by each stacked server instance. The general formula to determine the amount of processor that can be used by a single instance is: 100%/maximum_number_of_stacked_instances. For example, if you have three stacked server instances on a node, the workload is throttled to prevent any single server instance form using more than 33 percent of the processor.


Related concepts

  • Dynamic clusters


    Related tasks

  • Configure vertical stacking
  • Configure a dynamic cluster with homogeneous nodes to support vertical stacking
  • Configure a dynamic cluster with heterogeneous nodes to support vertical stacking