Analysis of a computer system with arbitrary distributions for h/w and s/w replacement time and priority to repair activities of h/w over replacement of s/w

The present paper deals with reliability and economic measures of a computer system introducing the concepts of inspection and priority to repair activities of the h/w over replacement of the s/w. The computer system has two identical units- one is operative and the other is kept as spare in cold standby. Each unit has h/w and s/w components which may fail completely directly from normal mode. The h/w and s/w components fail independently. There is a single server who visits the system immediately when needed to do inspection, repair and replacement of the h/w and s/w components. Sever inspects the unit at its h/w failure to see the feasibility of repair. If repair of the failed h/w components is not feasible, these are replaced by new one with some replacement time. However, only replacement of the s/w components in the unit is made by new one. Also, priority is given to replacement and repair of the h/w over replacement of the s/w components. The failure time of the unit follow negative exponential while the distributions of inspection, repair and replacement times of the h/w and s/w components are taken as arbitrary with different probability density functions (pdf). The expressions for some measures of system effectiveness are derived by using semi-Markov process and regenerative point technique. The numerical results for a particular case are also obtained to depict the graphical behaviour of MTSF, availability and profit with respect to h/w failure rate.