RELIABILITY EVALUATION FOR FAULT-TOLERANT SYSTEMS.

Important problems that arise in modeling highly-reliable fault-tolerant systems are discussed. First, reliability models of such systems possess a large number of states, making the solution computationally intractable. This leads to the need for decomposition/aggregation techniques, and several methods for approximate and exact aggregation are discussed. Second, the common assumption of exponential holding times in the states is intolerable while modeling such systems. Finally, errors in the reliability model and the solution techniques need to be identified and their effects on the model prediction need to be bounded.