This paper investigates a stochastic model developed for a two-unit cold standby hardware-software system considering fault tolerance characteristics. In the system, whenever hardware or software components of the operative unit fail, the cold standby unit is switched for operation and this leads to partial failure of the system. Further on hardware or software failures of the cold standby unit the system goes to complete failures. The fault detection and recovery coverages are also taken. The fault detection coverage is conditional probability of detecting a fault given that fault has occurred whereas the fault recovery coverage is conditional probability of recovery of a fault given that fault has occurred and has been detected. The partial failures are auto-recovered by software recovery mechanisms whereas upon complete failures external engineer is called. Various measures of performance of the system are obtained using Semi-Markov process and regenerative point techniques. The expected profit incurred to the system is also evaluated. Numerical results and graphical analysis pertaining to a particular case have been taken to make conclusions about the performance and cost-benefit of the system.
Hardware-software system, two-unit cold standby system, reliability, mean up time, mean degradation time, profit, semi Markov process and Regenerative point techniques
