Fault-tolerant Operating System Research Articles

Failure and Coverage Factors Based Markoff Models: A New Approach for Improving the Dependability Estimation in Complex Fault Tolerant Systems Exposed to SEUs

Dependability estimation of a fault tolerant computer system (FTCS) perturbed by single event upsets (SEUs) requires obtaining first the probability distribution functions for the time to recovery (TTR) and the time to failure (TTF) random variables. The application cross section (sigmaAP) approach does not give directly all the required information. This problem can be solved by means of the construction of suitable Markoff models. In this paper, a new method for constructing such models based on the system's failure and coverage factors is presented. Analytical dependability estimation is consistent with fault injection experiments performed in a fault tolerant operating system developed for a complex, real time data processing system.

Formal verification of safety‐critical systems

AbstractWe describe our practical experience in the use of formal verification to obtain increased confidence in the design of safety‐critical systems. The experiment involved demonstrating the consistency of the design specifications of SIFT, a software‐implemented fault‐tolerant operating system for aircraft flight control. Specifications were written at successive levels of abstraction from the most abstract requirements definition down to the detailed level of program code. Consistency of the successive levels of specification was demonstrated using the enhanced HDM verification system. Formal verification is currently feasible only for carefully simplified systems, but there appears to be no alternative method that can meet the extreme safety requirements for safety‐critical systems.