Summary & Conclusions -Despite the increasing need for ultra-reliable computers for use in distributed environments, there has been no significant advances to reduce the time overhead of combining replicated data in conjunction with providing instantaneous error masking. We propose two techniques that provide a compromise between the high time overhead in maintaining synchronous voting and the difficulty of combining results in asynchronous voting. These techniques are specifically suited for real-time applications with a single-source/single-sink structure that need instantaneous error masking. A description of the techniques, their underlying system requirements, and possible time bounds are presented. Two techniques provide a compromise between a tightly synchronized system in which the synchronization overhead can be quite high, and an asynchronous system which lacks suitable algorithms for combining the output data. Both QMV and CMV are most applicable to distributed real-time systems with singlesource/single-sink tasks. All real-time systems eventually have to resolve their outputs into a single action at some stage. The development of the Advanced Information Processing System (AIPS) and other similar systems serve to emphasize the importance of this class of real-time systems and the possible applications of these techniques. Time bounds suggest that it is possible to reduce the overhead for quorum-majority voting to below that for synchronous voting. All the bounds assume that the computation phase is non-preemptive and that there is no multi-tasking.
REF discusses the possibility to strike a balance between the overhead of tight synchronization and the algorithmic complexity of fully asynchronous operation via an intermediate approach.
Alternative majority-voting methods for real-time computing systems
IEEE Transactions on Reliability
Computer Science