Bounded approximate reliability models for distributed systems

A study is made of several methods for reducing complex fault tree models of fault-tolerant distributed systems. For each method the authors provide bounds on the estimate of unreliability that is obtained from the reduced model. They discuss methods for truncating the solution of a model expressed as a fault tree and then develop techniques that apply to the construction of the fault tree model. The emphasis is on producing approximate (but bounded) results applicable to realistic systems. The authors also discuss methods for incorporating dynamic system behavior (error handling and redundancy management) into fault tree models, and the corresponding truncated solution. The methods are presented as they are used in modeling two distributed systems, the Cm* system and AIPS (the Advanced Information Processing System)