Markov Renewal Theory Applied to Performability Evaluation

Computer and communication systems are designed to meet a certain speciied behavior. The procurement of metrics to establish how well the system behaves, that is, how closely it follows the speciied behavior , is the objective of quantitative analysis. Traditionally, performance and dependability evaluation are used as separate approaches to provide quantitative gures of system behavior. Performance evaluates the quality of service, assuming that the system is failure-free. 1 Dependability focuses on determining deviation of the actual behavior from the speciied behavior in the presence of component or subsystem failures. 2 Beaudry 3 proposed the aggregated measure computation before failure , while Meyer 4 proposed the term performability, which has been used since then. Performability analysis aims to capture the interaction between the failure-repair behavior and the performance delivered by the system. Its results are fundamental to the analysis of real-time system performance in the presence of failure. 5 Performability measures provide better insight into the behavior of fault-tolerant systems. Basic metrics used to evaluate fault-tolerant de