Availability, MTBF and MTTR for Repairable M out of N System

The availability of a redundant system requiring m out of n units to be operational represents a basic and elementary result within reliability engineering. The corresponding mean time between system failures (MTBF) and mean time of system restoral (MTTR) are less commonly known since these results have either required the solution of time-dependent system of equations or matrix algebra. This short paper shows that explicity results for the MTBF and MTTR performance are as easy to obtain as the availability for arbitrary m, n-values.