A framework for hardware-software tradeoffs in the design of fault-tolerant computers

Abstract

The theory of fault-tolerant computer design has developed rapidly. Several techniques using hardware or software have been suggested. A student is often faced with the problem of developing a common perspective for a variety of methods. In this paper we attempt to develop a simple framework within which different methods can be compared. We use a set of very elementary indices to construct the framework. The indices are quite crude and our framework is somewhat ad hoc. Though a unified theory would be extremely useful we have not attempted to develop one here. Our discussion is a first pass at identifying some goals of reliable design and an attempt at quantifying some parameters. We discuss only a very small set of the techniques that have been proposed for fault-tolerant computers. Methods for constructing relevant indices for these techniques are presented. We feel that these indices are relevant for most reliability techniques.