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Operating Systems: AIX, HP-UX, Linux, Solaris, Windows, z/OS

 

Determining the stacking number for a dynamic cluster


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

 

Before you begin

 

About this task

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

You can determine the stacking number by profiling of your application. If your dynamic cluster is homogeneous, and all of the nodes for the dynamic cluster have similar power, 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.

 

Procedure

  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 you 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 you can configure the stacking number in the administrative console.

  6. If your 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 your cluster. With vertical stacking enabled, the autonomic managers can limit the CPU percentage that is used by each stacked server instance. The general formula to determine the amount of CPU 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% of the CPU.


Next topic

Configure a dynamic cluster with homogeneous nodes to support vertical stacking

Next topic

Configure a dynamic cluster with heterogeneous nodes to support vertical stacking

 

Related concepts


Dynamic clusters

 

Related tasks

Configure vertical stacking