Keywords: software rejuvenation, preventive maintenance, redundant systems, switching mechanisms, partial rejuvenation, full rejuvenation, failed rejuvenation, system availability, downtime cost, dependability measures, optimal rejuvenation policy, modelling, critical computing
Semi-Markov performance modelling of a redundant system with partial, full and failed rejuvenation
Software rejuvenation is a preventive maintenance technique to prevent failures in continuously running systems that experience software aging. In this paper, rejuvenation is modelled in a redundant computer system via a Semi-Markov process in order to counteract software aging. An alternative rejuvenation modelling is also introduced, in which two different actions, partial and full rejuvenation, are performed according to the degradation level. Moreover, the case where software rejuvenation fails to fulfil its purpose leading to a failure is considered. System's asymptotic availability is studied with respect to the optimal time to perform rejuvenation. Additionally, the expected downtime cost, along with some dependability measures, is also studied. The main purpose of our work is to provide the appropriate framework for finding the optimal rejuvenation interval that will improve not only system's asymptotic availability but also the downtime cost and its performance.