WebSphere Application Server V8.5 Administration and Configuration Guide for the Full Profile

292 WebSphere Application Server V8.5 Administration and Configuration Guide for the Full Profile

 To add a node to a node group, display the node group, and click Node group members

in the Additional Properties section. When the list appears, click Add. You can select from

a list of nodes (Figure 7-48).

Figure 7-48 Displaying node group members

7.6 Working with clusters

This section provides information about creating, configuring, and managing application

server clusters using the administrative console.

Clusters consist of one or more application servers that run the same applications. The

configuration of each server can be unique.

Before creating a cluster, consider the number of servers you want to add to the cluster, the

nodes on which they will be created, and how the workload is distributed across the servers.

Work is distributed across the servers in the cluster based on weights assigned to each

application server. If all cluster members have identical weights, work is distributed among the

cluster members equally. Servers with higher weight values are given more work. An example

formula for determining routing preference is:

% routed to Server1 = weight1 / (weight_1 + weight_2 +...+ weight_n)

In the formula, n represents the number of cluster members in the cluster. Consider the

capacity of the system that hosts the application server.

7.6.1 Creating application server clusters

When you create a cluster, you have the option to create an empty cluster (no servers) or to

create the cluster with one or more servers. The first application server added to the cluster

acts as a template for subsequent servers. You can create the first server during the cluster

creation process, or you can convert an existing application server. The rest of the servers

must be new and can be created when you create the cluster or added later.

Tip: When creating a cluster, it is possible to select the template of an existing application

server for the cluster without adding that application server into the new cluster. If you need

to change the attributes of the servers in your cluster after the cluster is created, you must

change each server individually. For this reason, consider creating an application server

with the server properties that you want as a standard in the cluster first, then use that

server as a template or as the first server in the cluster.