This book presents a unique perspective on how terms such as GRID, cluster, parallel file system, reliability, availability, maintainability, and scalability are interrelated and how to quantify overall system stability in ever larger system environments that today may span around the globe. This book introduces the reader to the concepts, architectures, philosophies, and methodologies behind terms such as GRID, cluster, SAN, NAS, IO storage, or interconnect. While these terms appear in the literature on a regular basis, this book takes a unique approach, as it focuses on quantifying scalability, reliability, availability, and maintainability issues surrounding these rather large IT environments. The goal of this book is to illustrate how they are all linked together and hence how they have to be analyzed and quantified as a unit.