Combining Applications on the Same Cluster

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

When you create your Network Load Balancing design, one of the first steps is to determine if you can combine the applications and services in your solution on the same cluster. One of the primary concerns when combining applications on the same cluster is determining if the applications are compatible with each other. Table 8.1 lists the categories of common applications and services that run on Network Load Balancing, and it describes how you can combine them on the same cluster.

Table 8.1   Compatibility of Applications and Services on a Cluster

Application or Service Combined on the Same Cluster

IIS 6.0 Web applications
  • Can be combined on the same cluster; however, might require customized port rules.1

Terminal Services
  • Can run any combination of applications as long as the applications are compatible with Terminal Services.

  • Avoid combining Terminal Services (when Terminal Services is hosting applications) with other application platforms or services, such as IIS 6.0 or VPN remote access.2

VPN remote access
  • Can be combined with ISA Server to combine remote access server and firewall features in the same server.

  • Otherwise, avoid combining with other application platforms and services, such as IIS 6.0.

ISA Server
  • Can be combined with Routing and Remote Access to combine remote access server and firewall features.

  • Can be combined with IIS 6.0 to provide default Web site redirection to a Web site that is local to the server running ISA Server and IIS 6.0.

Custom applications
  • Can be combined on the same cluster; however, might require customized port rules.1

1 For more information, see "Identifying Applications or Services That Require Custom Port Rules" later in this chapter.

2 If you are not hosting applications with Terminal Services, you can combine Terminal Services with IIS 6.0 Web applications, VPN remote access servers, ISA Server, and your custom applications to provide remote administration of those servers.

As mentioned in Table 8.1, avoid running some applications and services, such as Terminal Services and VPN remote access, on the same cluster. The reasons for not running these applications and services on the same cluster include system resource constraints, security constraints, and ease of management.

In some instances, the cluster hosts might not have sufficient system resources to run the combined applications. For example, if you use Terminal Services to host applications, Terminal Services consumes a significant amount of processor and memory resources. Hosting applications with Terminal Services on the same cluster as IIS 6.0 might cause significant delays in running Web applications. For more information about scaling applications and services on Network Load Balancing clusters, see "Scaling NLB Solutions" later in this chapter.

Also, security considerations might require running the applications and services on separate clusters. For example, you might want to avoid running an FTP site that allows anonymous access on a cluster that also runs a secured e-commerce Web application.

Finally, combining applications on the same cluster can make the applications unmanageable and difficult to administer. The complexity of combining applications can correspondingly increase the complexity of managing and operating the cluster. For more information about creating clusters that are easy to manage and operate, see "Ensuring Ease of Cluster Management and Operations" later in this chapter.