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.
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, you must 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,
you 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,
you must profile each node and determine the stacking number for each node.
Procedure
- Start one server instance on the test node.
- View CPU utilization and average throughput curves for the node.
To view the charts,
click Runtime operations > Reports.
- Increase the load on the node, with the goal of reaching 90-100%
node utilization.
- 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%.
- 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.
- 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.