Planning your groups

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Planning your groups

You can take six steps to organize your applications and other resources into groups:

List all your server-based applications

Most groups contain one or more applications. Make a list of all applications in your environment, regardless of whether or not you plan to use them with the Cluster service. Your total capacity needs are determined by the sum of the total number of groups (virtual servers) that will run in your environment and the total amount of other software you will run independently of groups.

Sort the list of applications

Determine which of your applications can use failover. For more information, see Choosing applications to run on a server cluster.

Also list applications that will reside on cluster nodes but that will not use the failover feature because it is inconvenient, unnecessary, or impossible to configure the applications for failover. Although you do not set failover policies for these applications or arrange them in groups, they still use a portion of the server capacity.

Before clustering an application, review the application license, or check with the application vendor. Each application vendor sets its own licensing policies for applications running on clusters.

List all other resources

Determine which hardware, connections, and operating-system software a server cluster can protect in your network environment. For more information, see Addressing risks using server clusters.

For example, the Cluster service can fail over print spoolers, to protect client access to printing services. Another example is a file-server resource, which you can set to fail over, maintaining client access to files. In both cases, capacity is affected, such as the random access memory (RAM) required to service the clients.

List all dependencies for each resource

When you create this list, include all resources that support the core resources. For example, if a Web-server application fails over, the Web addresses and cluster storage devices containing the files for that application must also fail over if the Web server is to function. All these resources must be in the same group. This ensures that the Cluster service keeps interdependent resources together at all times.

Two guidelines for quantifying resources are:

• A resource and its dependencies must be together in a single group.

• A resource cannot span groups.

For example, if several applications depend on a particular resource, you must include all of those applications with that resource in a single group.

Make preliminary grouping decisions

Another factor in the way you assign groups is administrative convenience. For example, you might put several applications into one group because viewing those particular applications as a single entity makes it easier to administer the network.

A common use of this technique is to combine file-sharing resources and print-spooling resources in a single group. All dependencies for those applications must also be in the group. You can give this group a unique name for the part of your organization it serves, such as "Accounting File&Print." Whenever you need to intervene with the file- and print-sharing activities for that department, you would look for this group in Cluster Administrator.

Another common practice is to put applications that depend on a particular resource into a single group. For example, suppose a Web-server application provides access to Web pages, and that those Web pages provide result sets that clients access by querying a Microsoft SQL Server 2000 database application, through the use of Hypertext Markup Language (HTML) forms. By putting the Web server and the Microsoft SQL Server 2000 database in the same group, the data for both core applications can reside on a specific disk volume. Because both applications exist within the same group, you can also create an Internet protocol (IP) address and network name specifically for this resource group.

Make final grouping assignments

After you list the resources that you want to group together, assign a different name to each group, and create a dependency tree. A dependency tree is useful for visualizing the dependency relationships between resources.

To create a dependency tree, first write down all the resources in a particular group. Then draw arrows from each resource to each resource on which the resource directly depends.

A direct dependency between resource A and resource B means that there are no intermediary resources between the two resources. An indirect dependency occurs when a transitive relationship exists between resources. If resource A depends on resource B and resource B depends on resource C, there is an indirect dependency between resource A and resource C. However, resource A is not directly dependent on resource C.

The figure shows the resources in a final grouping assignment in a dependency tree.

In the diagram, the File Share resource depends on the Network Name resource, which, in turn, depends on the IP Address resource. However, the File Share resource does not directly depend on the IP Address resource.

For information on using Cluster Administrator to set resource dependencies, see Setting resource properties.