Unreliable two-server queueing system with variable repair rates

This article considers an infinite-capacity two-server queue system, where the servers are subject to failure at any time. A repairman is responsible for repair the failure server and the repair rate is changeable depending on the number of failure servers. The repair rate of only one server is failure and that of two servers are all failure may be different. The steady-state reliability indexes and the stability condition of queue are derived through the transfer rate matrix. The expected queue length and some related steady-state performances are obtained by the probability-generating function transform method. Numerical examples are provided for illustration purpose. © 2017 Chinese Institute of Industrial Engineers.