RAScad is a Sun internal Web-based reliability, availability, serviceability (RAS) architecture modeling and analysis tool for use in the computer system design and development phase. Two major goals of RAScad are: making availability modeling possible for design engineers without background in mathematical modeling and making availability modeling efficient for RAS engineers who understand underlying mathematical models. To achieve these goals, RAScad integrates two modules: Model Generator (MG) which provides automatic model generation specific to Sun product RAS characteristics, and Graphical Model Builder (GMB) which provides general, graphical Markov, semi-Markov and reliability block diagram modeling capabilities. An MG model is a hierarchical specification, in terms of an engineering language (MTBF, MTTR, redundancy, etc.), of the constituent components and associated parameters for the modeled system and the user does not have to understand the underlying mathematical models generated by RAScad.