4.1 Introduction

We begin by reviewing the content of the preceding chapters.

• Chapter 1,"Understanding Clusters and Your Needs," defined what a cluster is and what it is not.

• Chapter 2, "Crystallizing Your Needs for a Cluster," provided guidelines for your computer system's needs.

• Chapter 3, "Mechanisms of Clustering," discussed terms and tools used by clusters.

It is now time to see what type of cluster is best suited for your needs. Or, to rephrase, now that you've listed what you need and looked at some of the cluster mechanisms, it's time to look at what is available. With all the different ideas, methods, and implementations of "clusters," what kind of cluster is right? Let's take the information we have defined and described and attempt to classify "clusters" in accordance with their capabilities.

Clusters have been available since 1983. So, why haven't clusters been more commonplace? Naturally, money had a lot to do with it. More specifically, what was available from technology and at what cost? Sure, clusters have been available for quite awhile, but the downward spiral of the cost did not begin until 1993. Now that is an interesting year the year that Microsoft introduced Windows NT 3.1.

Now, more than ever, various vendors are offering various "cluster" systems and all claiming to be "the" cluster system. The problem is that there is such a diversity and choice, there is a need to sit down with paper and pencil, list what is needed, and determine whether the cost of satisfying...