Repairable 3-out-of-4: Cold standby system availability

Systems operating in risky environments strive for guaranteeing the highest possible availability. This paper addresses the effect of redundancy and components' economy of scale on achieving a high level of availability. An availability estimation model for a 3-out-4 cold standby system was developed and compared with 6-out-8 system. The analysis of the two models revealed that at relatively low availability target, using larger economic components results in higher availability. On the other hand, targeting an extremely high availability requires to scarify the components' economy of scale.