Calculation of a system reliability function is one of the principal problems in reliability theory. It is well known that even for the simplest double redundant repairable system this function has not been analytically calculated yet in case when elements reliability and recovery functions have general distributions. In current paper we study the reliability function and the mean time to failure of a homogeneous hot standby repairable system with exponential distribution of its elements life time and general distribution of their repair time. With the help of the developed general discrete-event simulation model we extend the previous studies to a general case of a homogeneous hot double redundant repairable system with general distributions of both life and repair time lengths of elements. It is shown that the results of exact analytical calculation and simulation results have close agreement.