Combining various solution techniques for dynamic fault tree analysis of computer systems

Fault trees provide a conceptually simple modeling framework to represent system-level reliability in terms of interactions between component reliabilities. DIFtree [1] effectively combines the best static fault tree solution technique (Binary Decision Diagrams) with Markov solution techniques for dynamic fault trees. DIFtree includes advanced techniques for modeling coverage; coverage modeling has been shown To be critical to the analysis of fault tolerant computer systems. DIFtree is based on a divide-and-conquer technique for modularizing the system level fault tree into independent sob-trees; different solution techniques can be used for sub-trees. In this paper we extend the DIFtree analysis capability to model several different distributions of time to failure, including fixed probabilities (no time component, exponential (constant hazard rate), Weibull (time varying hazard rate), and log normal. Our approach extends bath the BDD and Markov analytical approaches and incorporates simulation as well.