Talks & Seminars
Software Aging and Rejuvenation
Prof. Kishor Trivedi,,
Date & Time: March 12, 2003 16:00
Venue: Institute Auditorium
As society's dependence on computer systems increases, computer failures which result in significant losses will become more common. It has now been established that even for applications which have relatively less complex software, most failures in computer systems are due to software bugs. Hence, software reliability is one of the weakest links in system reliability. We will discuss the phenomenon of software aging that has been reported in widely used software and also in high-availability and safety-critical systems. To counteract this phenomenon, a proactive technique called "software rejuvenation" has been proposed. This essentially involves gracefully terminating an application or a system and restarting it in a clean internal state. We will discuss methods of evaluating the\Neffectiveness of software rejuvenation in operational software systems and determining optimal times to perform rejuvenation. This is done by developing stochastic models which tradeoff the cost of unexpected failures due to software aging with the overhead of proactive fault management. We will then describe measurement-based models which are constructed using workload and resource usage data collected from the UNIX operating system over a period of time. The measurement-based models are the first steps towards predicting aging related failures, intended to help development of strategies for software rejuvenation triggered by actual measurements. We have also recently extended the use of rejuvenation to cluster systems. Our analyses show that employing software rejuvenation in cluster systems results in a significant increase in system availability. Finally, we discuss the implementation of a software rejuvenation agent in a major commercial server.
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