Reliability growth of fault-tolerant software

The influence of reliability growth of the fault-tolerant software components on the reliability of the software system in operation is modeled and estimated. Two fault-tolerant software techniques are investigated: recovery block and N-version programming. For each, the stable reliability model is transformed into a model that considers reliability growth using a transformation approach based on the hyperexponential model. Analytic and numeric processing of the transformed models identify the influence of fault removal on the reliability of the fault-tolerant software approaches. The modeling approach is based on the transformation of a Markov chain of the fault-tolerant software system in stable reliability into another modified Markov chain that enables reliability growth to be considered. This approach allows reliability growth relative to the classes of faults affecting fault-tolerant software to be identified and evaluated. The evaluations apply to systems of short successive mission durations with respect to the system lifetime. Using generalized stochastic Petri nets to model the fault-tolerant software system allows for an automatic application of the transformation technique