Parallel Database Join Operations in Heterogeneous Grids

This paper presents an analytical comparison of parallel join algorithms in a generalized multiprocessor framework and a simplified, heterogenous Grid environment. We develop a concise but comprehensive analytical model for the well-known hash join algorithm and compare it to nested-loop and sort-merge join algorithms. We concentrate on a limited number of characteristic parameters to keep the analytical model clear and focused. We justify that a meaningful model can be built upon only three characteristic parameter sets, describing node processing performance, the I/O and the disk bandwidth, which are the parameters for the optimization the Grid workflow by a smart brokerage mechanism. Based on these results the paper proves that by a smart enhancement of the algorithms exploiting the specifics of the Grid the known performance results for a homogenous multi-processor architecture are to be revised for a heterogenous Grid environment.