OPTIMAL COST-EFFECTIVE DESIGN OF HYBRID HARDWARE REDUNDANT-SYSTEMS

In many critical applications of digital systems, fault tolerance has been an essential architectural attribute for achieving high reliability. We address the problem of designing an optimal hybrid hardware redundant system. The designer of a system is always confronted with the problem of trading off reliability against cost. On the one hand, it is essential to provide for each vital module of the system as many spare units as possible in order to ensure high reliability. On the other hand, it is essential not to have an excessively costly, heavy or bulky system. In this paper we determine the optimal number of spare units which minimizes the expected total system cost. A numerical example is provided to illustrate the methods.