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Comparing Software Rejuvenation Policies under Different Dependability Measures
Tadashi DOHI Hiroaki SUZUKI Kishor S. TRIVEDI
Publication
IEICE TRANSACTIONS on Information and Systems
Vol.E87D
No.8
pp.20782085 Publication Date: 2004/08/01 Online ISSN:
DOI: Print ISSN: 09168532 Type of Manuscript: PAPER Category: Dependable Computing Keyword: software rejuvenation, software aging, system availability, mean up rate, preventive maintenance, numerical optimization, fault management, design diversity,
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Summary:
Software rejuvenation is a preventive and proactive solution that is particularly useful for counteracting the phenomenon of software aging. In this paper, we consider both the periodic and nonperiodic software rejuvenation policies under different dependability measures. As is well known, the steadystate system availability is the probability that the software system is operating in the steady state and, at the same time, is often regarded as the mean up rate in the system operation period. We show that the mean up rate should be defined as the mean value of up rate, but not as the mean up time per mean operation time. We derive numerically the optimal software rejuvenation policies which maximize the steadystate system availability and the mean up rate, respectively, for each periodic or nonperiodic model. Numerical examples show that the real mean up rate is always smaller than the system availability in the steady state and that the availability overestimates the ratio of operative time of the software system.

