As you’ve learned in this chapter, Windows Server 2003 supports two distinct types of clustering: NLB clusters, which simply provide load distribution capabilities to certain IP-based applications; and true server clustering, which provides fault tolerance capabilities to larger sets of machines.
NLB is quite useful if you have a web-based application and several machines that can be devoted to servicing that application. The hardware does not need to be terribly powerful, and NLB is a great way to put used machines into service while providing a faster end-user experience. True server clustering is a better fit for medium-size organizations that have business-critical applications that always have to be available, no questions asked. Of course, with the high availability aspect comes increased cost, and the hardware investment required for true fault-tolerant capabilities is significant and should not be overlooked.