Adding members to a cluster

You create an application server as a member of a configured cluster.

Before you begin

You must create a cluster if you do not already have a configured cluster.

About this task

If you are migrating from a previous version of WebSphere Application Server, you can upgrade a portion of the nodes in a cell, while leaving others at the other release level. For a time, you might be managing servers that are at a previous release level and servers that are running at the newer release in the same cell.

In this mixed environment, some restrictions apply regarding what you can do with clusters and cluster members:
  • You cannot create a cluster member using a server that is running on WebSphere Application Server Version 5.x.
  • You cannot add a member that is running WebSphere Application Server Version 5.x to any cluster.

To create a new cluster member, view information about existing cluster members, or manage existing cluster members:

Procedure

  1. In the administrative console, click Servers > Clusters > cluster_name > Cluster members. The Cluster members page lists members of a cluster, and for each member indicates:
    • The node on which the member resides.
    • Whether the member is started, stopped, or encountering problems.
  2. Click New to create a new cluster member.
    1. Specify a name for the cluster member (application server). The name must be unique within the node.
    2. Select the node for the cluster member.
    3. Specify the server weight.

      The weight value you specify controls the number of requests that are directed to the application server. Even though you specify a value of 0 to 20 as the weight of a server, the weight that is given to the server as a member of a cluster is a proportion that is based on the weight assigned to the server (the numerator) and the sum of the weights of all members of the cluster (the denominator).

      When you add a new member to a cluster, the number of requests that are sent to each server in the cluster decreases, assuming the number of requests coming into the cluster stays the same. Similarly when you remove a new member from a cluster, the number of requests that are sent to each server in the cluster increases, assuming the number of requests coming into the cluster stays the same.

      For example, if you have a cluster that consists of members A, B, and C with weights 2, 3, and 4, respectively, 2/9 of the requests are assigned to member A, 3/9 are assigned to member B, and 4/9 are assigned to member C. If a new member, member D, is added to the cluster and member D has a weight of 5, member A now gets 2/14 of the requests, member B gets 3/14 of the requests, member C gets 4/14 of the requests, and member D gets 5/14 of the requests.

    4. Specify whether to generate unique HTTP ports.
    5. Specify the server template.
  3. Save your configuration. As part of saving the change to the configuration, you can select Synchronize changes with Nodes before clicking Save on the Save page.

Results

You created application servers that are members of an existing server cluster.

What to do next

If when you created the new members, you chose to generate unique ports, update the alias list for the virtual host that you plan to use with the new servers.

You can:




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Last updated: Sep 20, 2010 9:00:59 PM CDT
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