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Summary: Performance Evaluation 46 (2001) 4562
Fine grained software degradation models for
optimal rejuvenation policies
Andrea Bobbioa, Matteo Serenob,, Cosimo Anglanoa
a
Dipartimento di Scienze e Tecnologie Avanzate (DISTA), Universitą del Piemonte Orientale,
Corso Borsalino 54, 15100 Alessandria, Italy
b
Dipartimento di Informatica, Universitą di Torino, Corso Svizzera 185, 10149 Torino, Italy
Received 19 May 1999; received in revised form 6 March 2001
Abstract
In this paper, we address the problem of preventive maintenance of operational software systems, an approach recently pro-
posed to counteract the phenomenon of software "aging". We consider the so-called "software rejuvenation" technique [Soft-
ware rejuvenation: analysis, module and applications, in: Proceedings of the 25th International Symposium on Fault-Tolerance
Computing (FTCS-25), Pasadena, CA, USA, June 1995], which consists in periodically stopping the software system and
then restarting it in a "robust" state after a proper maintenance, and we propose a methodology for the quantitative analysis
of rejuvenation strategies. The methodology is based on a fine grained model that assumes that it is possible to identify the
current degradation level of the system by monitoring an observable quantity, so that the rejuvenation strategy can be tuned
on the measured degradation. Based on this methodology, we present two different strategies that allow to decide whether and
when to rejuvenate, and we exploit the theory of renewal processes with reward to estimate the steady-state unavailability of
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