Performance evaluation of three logging schemes for a shared-nothing database server

Abstract

The European declarative system (EDS) is a high performance backend database server designed for a range of commercial mainframes. One major application domain of EDS is information processing for business and commercial environments. High performance is achieved by exploiting parallelism using a shared-nothing Computer (up to 256 processors) and by reducing data access latency using large main memory storage (up to 4 Gbytes per PE) to hold the entire database in memory at processing time. Reliability is a crucial design issue for commercial and business information systems. Recovery control facilitates reliability and logging forms an important part of it. In general, logging is costly to implement; it is usually achieved in the expense of reduced system performance. A desirable logging scheme should not overload the database management system resulting in poor system performance. Three logging schemes have been studied for EDS: 1. (a) local discs — adopt a conventional approach by incorporating a local disc on each processor; 2. (b) duplexing — arrange the processors in pairs, one for database operations and one for backup; and 3. (c) cooperative logging similar to duplexing except database and backup operations are performed on a single processor. The performance of these schemes for on-line transaction processing was evaluated and compared using the EDS behavioral simulator. The results of the evaluations are presented in this paper. The results indicate that the cooperative logging scheme performs best amongst the three alternatives, but an EDS server based on this scheme can only achieve 70% of the performance target.