Semi-Markov Availability Modeling of a Redundant System with Partial and Full Rejuvenation Actions

Software rejuvenation is a preventive maintenance technique to prevent failures in continuously running systems that experience software aging. In this paper, rejuvenation is modeled in a redundant computer system via a semi-Markov process in order to counteract software aging. The system can be switched into the standby unit automatically or manually in the case of a failure at the switching mechanism. Depending on the degradation of the system resources, the running node is either rejuvenated or continues serving and systempsilas steady-state availability is studied along with the optimal time to perform rejuvenation, which increases systempsilas availability. Moreover, an alternative rejuvenation modeling is introduced, in which two different actions; partial and full rejuvenation are performed according to the degradation level. The optimal rejuvenation policies for this case are also derived, leading the system to higher levels of availability.