Modeling and analysis of system dependability using the system availability estimator

This paper reviews the System Availability Estimator (SAVE) modeling program package. SAVE is used to construct and analyze models of computer and communication systems dependability. The SAVE modeling language consists of a few constructs for describing the components in a system, their failure and repair characteristics, the interdependencies between components, and the conditions on the individual components for the system to be considered available. SAVE parses an input file and creates a Markov chain model. For small models numerical solution methods can be used, but for larger models (the state space grows exponentially with the number of components in the model), fast simulation techniques using importance sampling have to be used. We provide software demonstrations using both these techniques.