Implementation and Evaluation of the Bucket Flattening Omega Network of the Parallel Relational Database Server SDC-II

摘要

This paper presents the implementation and performance evaluation of the Bucket Flattening Omega Network of the SDC-II, the Super Database Computer II. The SDC-II is a highly parallel relational database server, which consists of eight data processing modules interconnected by two networks. Parallelism in the parallel relational database processing on the shared nothing architecture would suffer from skewed data distribution and collisions in the interconnection networks. The network of the SDC-II was designed to offer an architectural support of the Bucket Spreading hash join algorithm, which enables the system to have linear performance scalability even with skewed data distributions. The addiitonal functionality introduced into the network can generate a flat bucket distribution, which is essential to the algorithm, while providing almost conflict free routing. Each switching unit of the network is implemented on an FPGA chip, and its performance is evaluated to compare with an implementation without hardware supprot. The evaluation results show that the effective bandwidth of the latter implementation degrades to almost half of the ideal bandwidth, while little degradation is observed with the hardware support during all-to-all communication phase of the algorithm.