WebSphere Extended Deployment, Version 6.0.x
             Operating Systems: AIX, HP-UX, Linux, Solaris, Windows, z/OS


Creating dynamic clusters

When you create a dynamic cluster, weights are used to dynamically balance the workloads of the cluster members, based on performance information that is collected from the cluster members.

Before you begin

Complete the following prerequisites before creating a dynamic cluster:

About this task

A dynamic cluster is an application deployment target that can expand and contract depending on the workload in your environment. Dynamic clusters work with autonomic managers, including the application placement controller and the dynamic workload manager to maximize the use of your computing resources. Dynamic clusters are required for many of the product autonomic functions, including high availability and service policies.

When you create a dynamic cluster of application servers, the recommendation is to have a maximum number of 50 application servers, node agents, and on demand routers per core group. A dynamic cluster cannot span multiple core groups. Consider this limit when you set the number of instances and stacking number for your dynamic cluster. This limitation does not apply to dynamic clusters of assisted life-cycle servers or complete life-cycle dynamic clusters of PHP or servers.

Procedure

  1. Create the dynamic cluster. In the administrative console, click Servers > Dynamic clusters > New.
  2. Enter dynamic cluster information. In this step you give a name to the dynamic cluster, specify the node group to which the dynamic cluster is mapped, and define other dynamic cluster properties.
  3. Select a dynamic cluster template. You can either build servers that are based on a default template, or you can use an existing server from your environment as the template. The displayed templates are valid for the platform that corresponds to the node group that you selected for your dynamic cluster. The template also corresponds to the version of your deployment manager.
  4. Specify dynamic cluster-specific properties.
    1. Define the minimum number of cluster instances. The default minimum number of instances is one instance and the maximum default is no limit on instances.
    2. Define the maximum number of cluster instances. The default value has no limit on the number of cluster instances.
    3. Determine whether to enable vertical stacking. When you configure vertical stacking, more than one dynamic cluster instance can start on the same node.
  5. Confirm the dynamic cluster creation. Click Finish > Save to save the changes to the master configuration.
  6. Select the mode of operation. In the administrative console, click Servers > Dynamic clusters. Select the dynamic clusters that you want to modify. Choose the operational mode and click Set mode.
    Important: To use dynamic application placement, click Automatic or Supervised as the mode of operation.

    [For z/OS operating system] [Version 6.0.1 and later] If you have nodes that run on z/OS® systems, use dynamic clusters in supervised or automatic mode. If you want to prevent WebSphere® Extended Deployment from automatically starting a cluster member on a logical partition (LPAR) that is hosting a dynamic cluster when the LPAR processor is too busy, then you must define the cpuUtilizationThreshold custom property. In this scenario, the product starts the cluster member only if transaction demand requires additional cluster members and the processor utilization on the LPAR is less than the cpuUtilizationThreshold value. See cpuUtilizationThreshold for more information.

Results

[Version 6.0 only] The application placement controller starts a cluster instance on each node for the dynamic cluster. Cluster instances starts one server on each node concurrently across all of the nodes in the node group for your cluster. When all of the instances for the dynamic cluster are started, the cluster instances for another dynamic cluster in your environment can begin to start.

[Version 6.0.1 and later] When the dynamic clusters start, at least one instance of each dynamic cluster in your environment becomes available as soon as possible. Multiple instances on the same node can start concurrently if you have multiple processors on the same node. For example, if you have two processors on a node, two instances can start concurrently. The application placement controller continues to start instances evenly across the nodes for all the dynamic clusters until the minimum number of instances for each dynamic cluster is reached.

Example

Use the following placement scenarios as a guideline for your dynamic cluster settings:

What to do next

Remember: To change your server ports after the server has been created, you must change the ports on each server instance. You cannot change the ports through the dynamic cluster template. Because multiple servers can be on the same node by configuring vertical stacking, the ports must be unique for each server instance.



Subtopics
Dynamic clusters
Application lazy start
Static clusters versus dynamic clusters
Configuring vertical stacking
Related concepts
Components of dynamic operations
Related tasks
Deploying applications with defined service levels
Related reference
Administrative roles and privileges
Related information
Application placement custom properties
Task topic    

Terms of Use | Feedback

Last updated: Oct 16, 2009 11:06:12 AM EDT
http://publib.boulder.ibm.com/infocenter/wxdinfo/v6r0/index.jsp?topic=/com.ibm.websphere.xd.doc/info/odoe_task/todrdynamiccluster.html