3.1 Introduction

The preceding chapter on "cluster needs" introduced the capabilities and possibilities of cluster systems. And, certainly the terms availability, scalability, and reliability seem a little easier to understand. But what about the "how" the way these capabilities come about from within the cluster subsystems? Consider how the components of a clustered system work together as you would the elements of a football game.

In football, the principal goal is for a team of persons to carry a football from one end of a field to another, repeatedly, while fending off opponents who try to prevent this from happening. At any one time, only one person has the ball. That person's fellow team players will position themselves and work to present the best possible avenue for the ball carrier to succeed. Some players will work to provide a reliable block to the opposition, while others will avail themselves to the ball carrier in case the ball carrier is attacked or becomes unavailable. Each team member has a specialized job to help ensure that the goal is met. Woe to the team with the "individual" player. Anyone who has seen or played in team sports has seen the player who is absolutely convinced that only one can meet the goal himself. The goal on the football field is always attained by the team whose members act as one and yoke their common strengths and abilities. Certain members of the team have "backup." For example, there are two guards,...