NUMERICAL EVALUATION OF PERFORMABILITY AND JOB COMPLETION TIME IN REPAIRABLE FAULT-TOLERANT SYSTEMS.

Fault-tolerant computer systems change their level of performance (e. g, mode of operation or service rate) in response to different events such as failure, degradation or repair. The authors present a unified model for the analysis of job (task) completion time and performability (i. e. , the accumulated service (reward) until a given time). Several models have previously been developed elsewhere, however the evaluation of the distribution of performability was restricted to nonrepairable systems (represented by acyclic Markov chains). Here, the authors describe a single algorithm for the combined numerical evaluation of the distributions of performability and job completion time in repairable fault-tolerant systems (represented by cyclic Markov chains). The feasibility of the techniques is demonstrated by numerical examples.