Availability and Comparison of Spare Systems with a Repairable Server

This article analyzes availability characteristics among three various spare system configurations. Each configuration includes various amount of primary and warm standby units, and an unreliable server is responsible for repairing the failed units. The server may fail or break-down when it is repairing. Additionally, it is assumed the server’s time to break-down has exponential distribution. When the primary unit fails, the standby unit replaces it immediately where the replacement is perfect. The repair time of the failed units and the recovery time of the break-down server follow a random variable. Next, a useful model is built based on the three system configurations. We develop the explicit expressions of availability measures among three spare system configurations. The cost/benefit is also compared among three configurations with given to the distribution parameters, and to the cost of the primary and warm standby units.