Optimal software rejuvenation for tolerating soft failures

In recent studies, the phenomenon of software "aging" has come to light which causes performance of a software to degrade with time. Software rejuvenation is a fault tolerance technique which counteracts aging. In this paper, we address the problem of determining the optimal time to rejuvenate a server type software which experiences "soft failures" (witnessed in telecommunication systems) because of aging. The service rate of the software gradually decreases with time and settles to a very low value. Since the performability in this state is unacceptable, it is necessary to "renew" the software to its peak performance level. We develop Markov decision models for such a system for two different queuing policies. For each policy, we define the look-ahead-n cost functions and prove results on the convergence of these functions to the optimal minimal cost function. We also prove simple rules to determine optimal times to rejuvenate for a realistic cost criterion. Finally, the results are illustrated numerically and the effectiveness of the MDP model is compared with that of the simple rules.

Duke Scholars

Author Kishor S. Trivedi Electrical and Computer Engineering