Comparison of reliability and the availability between four systems with warm standby components and standby switching failures

Four different system configurations with warm standby components and standby switching failures are compared based on their reliability and availability. The time-to-repair and the time-to-failure for each of the primary and warm standby components are assumed to follow the negative exponential distribution. We develop the explicit expressions for the mean time-to-failure, MTTF, and the steady-state availability, AT(∞), for four configurations. For all four configurations, comparisons are made for specific values of distribution parameters and of the cost of the components. The configurations are ranked based on MTTF, AT(∞), and cost/benefit where benefit is either MTTF or AT(∞).