This example-driven, easy-to-read exploration of capacity planning of computer systems is designed to be accessible and relevant both to practising professionals and those with little mathematical background. Each chapter begins with an example, then guides the reader through the solution of the original problem via the solution of several smaller and simpler problems. In each case, the solution is based upon first principles and intuition. It draws examples from three current computing environments - centralized systems, distributed systems and parallel processing systems. The book is accompanied by a disk containing a modified version of QSolver/1, a capacity planning modelling package.