Static clusters versus dynamic clusters

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

Static clusters versus dynamic clusters

Static clusters in a WebSphere^® Application Server Network Deployment configuration are different from the dynamic clusters that you can define in WebSphere Virtual Enterprise. Both types of clusters support workload balancing, however, dynamic clusters are controlled by autonomic managers that can optimize the performance of the cluster.

Static cluster

A static cluster is a group of application servers in a WebSphere Application Server Network Deployment environment that participates in workload management.

Dynamic cluster

A dynamic cluster is a fundamental building block of the dynamic operations environment. You must configure dynamic clusters to get WebSphere Virtual Enterprise functionality, such as high availability and service policies.

Table 1. Static clusters versus dynamic clusters

Characteristic Static clusters Dynamic clusters

Membership You must manually add application servers to static clusters.
You can automatically define cluster members with rules or you can manually define the cluster members. If you are using servers that have complete life-cycle management, you can create a membership policy that automatically selects nodes on which to host dynamic cluster members based on different node properties. If you are using servers that have assisted life-cycle management, you can statically define the servers that are cluster members.
Cluster management You define the application servers that are in the static cluster and then start or stop all the application servers in the cluster. A dynamic cluster can start and stop instances of servers as required. If the dynamic cluster is in automatic mode, then the server instances stop and start automatically. If the dynamic cluster is in supervised mode, runtime tasks generate to advise the administrator to start and stop servers at certain times. In manual mode, the administrator decides when instances of servers are stopped and started.
Cluster templates When you define a static cluster, you can select an application server template on which to base all the application server instances that you create. However, any changes that you make to the template after creating the instances do not change the instances.
When you define a dynamic cluster, you can define an application server template for the application server instances.
After you define the dynamic cluster, you can use the dynamic cluster server template to edit the cluster member properties. The changes are propagated to all of the application server instances.
Application server weights You explicitly assign a weight value to each application server instance. You can also enable the dynamic workload manager to assign weight values. To enable the dynamic workload manager, click Servers > Clusters > cluster_name > Dynamic WLM. The dynamic workload manager is enabled by default and assigns weights to the application server instances. To disable the dynamic workload manager, click Servers > Clusters > cluster_name > Dynamic WLM.
Applicability You can use static clusters in a WebSphere Application Server Network Deployment environment, or a WebSphere Virtual Enterprise environment. If you use static clusters in a WebSphere Virtual Enterprise environment, then the behavior is identical to static clusters in a WebSphere Application Server Network Deployment environment. You can use dynamic clusters in a WebSphere Virtual Enterprise environment only.

Related concepts

Dynamic clusters

Related tasks

Creating dynamic clusters

Related reference

Dynamic cluster administrative tasks

Characteristic	Static clusters	Dynamic clusters
Membership	You must manually add application servers to static clusters.	You can automatically define cluster members with rules or you can manually define the cluster members. If you are using servers that have complete life-cycle management, you can create a membership policy that automatically selects nodes on which to host dynamic cluster members based on different node properties. If you are using servers that have assisted life-cycle management, you can statically define the servers that are cluster members.
Cluster management	You define the application servers that are in the static cluster and then start or stop all the application servers in the cluster.	A dynamic cluster can start and stop instances of servers as required. If the dynamic cluster is in automatic mode, then the server instances stop and start automatically. If the dynamic cluster is in supervised mode, runtime tasks generate to advise the administrator to start and stop servers at certain times. In manual mode, the administrator decides when instances of servers are stopped and started.
Cluster templates	When you define a static cluster, you can select an application server template on which to base all the application server instances that you create. However, any changes that you make to the template after creating the instances do not change the instances.	When you define a dynamic cluster, you can define an application server template for the application server instances. After you define the dynamic cluster, you can use the dynamic cluster server template to edit the cluster member properties. The changes are propagated to all of the application server instances.
Application server weights	You explicitly assign a weight value to each application server instance. You can also enable the dynamic workload manager to assign weight values. To enable the dynamic workload manager, click Servers > Clusters > cluster_name > Dynamic WLM.	The dynamic workload manager is enabled by default and assigns weights to the application server instances. To disable the dynamic workload manager, click Servers > Clusters > cluster_name > Dynamic WLM.
Applicability	You can use static clusters in a WebSphere Application Server Network Deployment environment, or a WebSphere Virtual Enterprise environment. If you use static clusters in a WebSphere Virtual Enterprise environment, then the behavior is identical to static clusters in a WebSphere Application Server Network Deployment environment.	You can use dynamic clusters in a WebSphere Virtual Enterprise environment only.