A comparative analysis of hardware and software fault tolerance: Impact onsoftware reliability engineering

Today's digital systems are growing increasingly complex, and are being use d in increasingly critical functions. The first premise makes them more pro ne to contain faults, and the second premise makes their failure less toler able. This widening gap highlights the need for fault tolerant techniques, which make provisions for reliable operation of digital systems despite the presence and occasional manifestation of faults. In this paper we present a brief comparative survey of fault tolerance as it arises in hardware syst ems and software systems. We discuss logical models as well as statistical models of fault tolerance, and use these models to analyze design tradeoffs of fault tolerant systems.