Clusters and Clustering is a popular form of distributed computing that ties together several UNIX machines which allow them to provide greater availability and flexibility of information. This text introduces Hewlett-Packard's Cluster architecture, known as the High Availability Cluster. Assuming no prior knowledge of Clusters, the book provides an accessible introduction to the terminology, issues, architectures, and solutions for building high availability systems and clusters. The hardware and software technologies and the costs associated with each are explained, and a discussion of what is involved is also provided.