Stochastic disaster recovery systems with external resources

This paper deals with a complex reliability system of main unreliable, spare, and auxiliary spare machines, subject to random breakdowns, repairs, and two replacement policies: one for busy, and another for idle or vacation periods. During vacation periods, when the system performs a mandatory routine maintenance, auxiliary machines are being used for back-ups; the information on the system is naturally delayed. We utilize an analog of the N-policy to restrict the usage of auxiliary machines to some reasonable quantity. Analytically, tractable results are obtained by using a duality principle (which enables us to treat a more rudimentary system), semiregenerative analysis, and the theory of fluctuations of multivariate marked renewal processes. The results are demonstrated in the framework of optimization problems.