QUEUEING ANALYSIS OF FAULT-TOLERANT COMPUTER SYSTEMS.

The failure/repair behavior of the server is modeled by an irreducible continuous-time Markov chain. Jobs arrive in a Poisson fashion to the system and are serviced according to first-come, first-served discipline. A failure may cause the loss of the work already done on the job in service, if any; in this case the interrupted job is repeated as soon as the server is ready to deliver service. In addition to the delays due to failures and repairs, jobs suffer delays due to queuing. An exact queuing analysis of the system is presented, and the steady-state behavior of the number of jobs in the system is studied. As a numerical example, a system with two processors subject to failures and repairs is considered.