Database Processing with Triple Modular Redundancy
N-Modular Redundancy (NMR) protects against arbitrary types of hardware or software failures in a minority of system components, thereby yielding the highest degree of reliability. In this paper we study the application of NMR, specifically Triple Modular Redundancy (TMR), to general-purpose database processing. We discuss the structure and implementation tradeoffs of a TMR system that is "synchronized" at the transaction level. That is, complete transactions are distributed to all nodes, where they are processed independently, and only the majority output is accepted. We examine the
inherent "cost" of such a TMR database system by presenting preliminary performance results from a version implemented on three SUN-2/120 workstations.