Hierarchical architecture for parallel query processing on networks of workstations

Networks of workstations (NOWs) are cost-effective alternatives to multiprocessor systems. Recently, NOWs have been proposed for parallel query processing. Idle CPU cycles of workstations in a NOW-based system can be used to process database query operations. We report on the performance of the hierarchical architecture for parallel query processing on a NOW. We have implemented the hierarchical architecture using PVM on a Pentium-based NOW. The experimental results reported suggest that the hierarchical architecture is successful in achieving good scale-ups and speedups indicating that the idle processor cycles are effectively used for query processing. The hierarchical system can also handle both light and heavy workloads in a load sharing fashion. Our results also suggest that the performance is sensitive to the minimum fragmentation size (chunk size) for partial operations and the structure of queries.