Modeling and analysis of software aging and rejuvenation

Software systems are known to suffer from outages due to transient errors. Recently, the phenomenon of “software aging”, one in which the state of the software system de-grades with time, has been reported. To counteract this phe-nomenon,a proactive approach of fault management, called “software rejuvenation”, has been proposed. This essen-tially involves gracefully terminating an application or a system and restarting it in a clean internal state. In this paper, we discuss stochastic models to evaluate the effec-tiveness of proactive fault management in operational soft-ware systems and determine optimal times to perform re-juvenation, for different scenarios. The latter part of the paper deals with measurement-based methodologies to de-tect software aging and estimate its effect on various system resources. Models are constructed using workload and re-source usage data collected from the UNIX operating sys-tem over a period of time. The measurement-based models are intended to help development of strategies for software rejuvenation triggered by actual measurements. 1