An Extended Reliability Evaluation Framework for computer systems using fuzzy logic

Most existing reliability analyses provide a quantitative assessment of the overall system reliability assuming that the components of a system can operate only in two modes: completely operational or non-operational. We have developed an Extended Reliability Evaluation Framework (X-REF) to compute the system reliability in a quantitative form as well as in a qualitative form. In the extended framework, the components of a computer system can operate in any number of degraded modes of operation. The state of a component is given by a reliability profile which represents the component´s reliability values and their associated degree of certainty. The inputs needed for X-REF are component reliability profiles and the fault tree of the system. An effective technique is developed to combine these component reliability profiles using the fault tree as a configuration to represent system failure for computing the overall reliability profile of the system