Architecture of fault-tolerant computers: an historical perspective

The author surveys the approaches and techniques used to improve system reliability. Over the past 40 years computing systems have experienced over three orders of magnitude improvement in average time to failure and over six orders of magnitude improvement in work accomplished between outages. A three-dimensional design space for comparing fault-tolerant systems is proposed and populated by over two dozen actual systems. A detailed description is provided for a dozen systems evenly distributed throughout the design space. The author concludes by observing trends in the design space and projecting future developments