Reliability analysis of fault tolerant recovery blocks

Reliability models for fault tolerant recovery blocks with exponential execution time are analysed. Explicit expressions for the reliability of independent recovery block with exponential execution time are derived. The paper presents conditions for the optimal arrangement of versions within a recovery block. The paper also presents two optimisation models for the independent recovery blocks with exponential execution time. The objective is to maximise the reliability of the fault tolerant software satisfying a budget constraint and a constraint on the mean execution time of the software. Simple branch and bound procedures are developed that can be used to solve the optimisation problem.