COM+ Application Cluster

A COM+ application cluster processes COM+ application requests for clients. These clients can include Windows-based clients and Web clusters. A COM+ application cluster relieves Web clusters and Windows-based clients from processing COM+ components. To support Windows-based clients by using DCOM, the cluster can use NLB or other load balancers to distribute incoming client requests. The following illustration shows a COM+ application cluster that is running NLB.

You can create Web clusters that use CLB to load balance the activation requests for COM+ components, and forward these requests from the Web cluster to the COM+ application cluster for processing. In a two-tier Application Center clustering environment, one tier handles requests for Web sites while the second tier handles requests for COM+ components. The performance for this environment may not match the performance of a single Web cluster because data must be transmitted between the Web cluster and COM+ application cluster. While the best performance is achieved by activating COM+ applications locally, creating a separate cluster to process COM+ components has the following advantages:

  • Increased security because you can place firewalls between Web clusters and COM+ application clusters so that clients accessing the Web cluster are restricted from accessing the COM+ application cluster.

  • If the COM+ applications consume extensive processing resources, Web servers may become unresponsive. You can create a separate COM+ application cluster to relieve the Web cluster of processing these COM+ applications. Since the Web cluster does not process the COM+ applications, it can achieve better performance in serving Web sites.

  • Increased manageability of server applications because COM+ applications are isolated on a separate cluster from Web clusters. The two separate clusters allow you to have different developers and administrators maintaining each cluster independently.

  • Support for clients of mixed environments; COM+ application clusters can accept requests from both clients accessing the Web cluster and clients running Windows-based applications.

To configure a two-tier Application Center cluster where one tier handles requests for Web sites and another tier processes COM+ components, you must complete the following steps:

  1. Create a Web cluster and a COM+ application cluster.

  2. Install the COM+ applications on both clusters.

  3. On the Web cluster:

    • Use the Component Services snap-in to enable dynamic load balancing support for the components you want load balanced by CLB.

    • Restart the COM+ component load balancing service.

    • Configure the COM+ routing list to include each of the members comprising the COM+ application cluster.

  4. On the COM+ application cluster, disable dynamic load balancing support for each component.

As clients send activation requests for COM+ components, the Web cluster determines if the components support dynamic load balancing and if so, forwards the request to one of the COM+ application cluster members on the routing list.

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