OpenSESAME - the simple but extensive, structured availability modeling environment

This article describes the novel stochastic modeling tool OpenSESAME which allows for a quantitative evaluation of fault-tolerant High-Availability systems. The input models are traditional reliability block diagrams (RBD) which can be enriched with inter-component dependencies like failure propagation, failures with a common cause, different redundancy types, and non-dedicated repair. OpenSESAME offers a novel set of graphical diagrams to specify these dependencies. Due to the dependencies, traditional solution methods for RBDs cannot be applied to OpenSESAME models. We therefore present a novel evaluation method, which is based on the automatic generation of several state-based models, which are semantically equivalent Preprint submitted to Elsevier 8 March 2007 to the high-level input model. Alternatively, either stochastic Petri nets or textual models based on a stochastic process algebra can be generated. The state based models are then analyzed using existing solvers for these types of models. Three case studies exemplify the modeling power and usability of OpenSESAME.