EVALUATION AND COMPARISON OF FAULT-TOLERANT SOFTWARE TECHNIQUES

Various fault-tolerant software techniques have been proposed in order to meet the reliability requirements of critical systems. This paper evaluates 4 implementations of fault-tolerant software techniques with respect to hardware and design faults. Project participants were divided into 4 groups, each of which developed fault-tolerant software based on a common specification. Each group applied one of the following techniques: n-version programming, recovery block, concurrent error-detection, and algorithm-based fault tolerance. Independent testing and modeling groups within the project then thoroughly analyzed the fault-tolerant software. Using fault-injection tools, the testing group subjected the fault-tolerant software to simulated design and hardware faults. Simulated design-faults included control flow, array boundary, computational, and post/pre increment/decrement software mutations. Simulated hardware-faults included code and data corruption. Data collected from the fault-injection experiment were then mapped into a discrete-time Markov model developed by the modeling group. Based on this model, the effectiveness of each implementation of the fault-tolerant software technique with respect to availability, correctness, and time to failure given an error, is contrasted with measured data. Finally, the model is analyzed with respect to additional figures of merit identified during the modeling process, and the techniques are ranked using an application taxonomy.