Windows 2000 Performance Guide

Load Balancing and Server Clustering

When you are finally convinced that your IIS server has reached its maximum capacity in servicing requests and have squeezed every ounce of performance out of each of the subsystems, there is yet another way to improve performance. Just like using a multiprocessor when your CPU subsystem is overworked or a RAID device when your disk subsystem is the bottleneck, you can use multiple physical machines to support a single logical web server. There are a number of ways to do this, ranging from a simple, low-cost solution such as round-robin DNS to a more sophisticated solution such as the Windows Load Balancing Service (WLBS). In addition to the performance benefits, using multiple physical servers provides enhanced fault tolerance. In this section, we describe three alternatives that are available for combining the processing power of multiple servers to provide a single, logical, high-performance web server.

The first option is the use of round-robin Domain Name System (DNS) for load distribution across multiple servers. The DNS server is a hierarchical and distributed database that provides both forward and reverse mapping of hostnames to IP addresses. For details on how to set up DNS and how it works, look at DNS on Windows NT by Paul Albitz, Matt Larson, and Cricket Liu, or DNS and BIND, by Paul Albitz and Cricket Liu (both from O’Reilly).

When the IIS server is installed and configured, A and PTR records are added to the DNS server. This ...