Load Balancing Options

There are two load-balancing options that you can use on any cluster you create with Application Center:

• Network Load Balancing (NLB)—This native Windows 2000 Advanced Server load-balancing mechanism distributes IP-based client requests across a cluster of Web servers.

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  Although it's not included with Windows 2000 Server, NLB is automatically installed on a system running Windows 2000 Server when Application Center is installed on the system.

• Component Load Balancing (CLB)—This native Application Center load-balancing mechanism distributes client requests for component instance creations across a cluster of COM+ application servers.

And, of course, there's also the option of not using load balancing on a cluster. In some scenarios—for example, a small testing and staging environment—you can disable load balancing because it really isn't needed. There are also times during synchronization and monitoring when it's desirable to have load balancing temporarily disabled for a member.

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You can choose to not use either NLB or CLB if you're running a third-party load balancing solution. You can continue to use your existing load balancer, but Application Center doesn't support managing these devices out-of-the-box. However, device-enabling solutions have been developed for selected load balancers. These solutions are documented in Chapter 13, "Third Party Load Balancer Support." If the load balancer that you're using isn't currently supported, you will have to develop custom scripts to enable communication between the load balancer and Application Center.

One of the guiding principles of the Application Center design is robust support for arm's length administration—which is to say, an administrator does not have to physically go to a member to set up or re-configure its load balancing behavior. The Application Center user interface simplifies configuration by abstracting away the details of the different load balancing options.