Optimal Inspection First and Last Policies for a Computer System

When a computer system executes successive jobs and processes with random time intervals, it would be impossible or impractical to make some inspections to check faults that occur intermittently in a strict periodic fashion. From such a viewpoint, by considering both factors such that periodic and random inspections, this paper proposes two new inspection policies in which the computer system is checked at a planned time T or at a random time Y, whichever occurs first and last. These policies are called inspection first and inspection last, respectively. Expected cost rates of each model until failure detection are obtained, and optimal inspection policies which minimize them are derived analytically. The comparison results of such two policies indicate that either inspection first or last is better than the other according to the ratio of checking cost to downtime cost from failure to its detection.