Performance evaluation of functional disk system with nonuniform data distribution

The performance of a functional disk system with relational database engine (FDS-RII) for a nonuniform data distribution is analyzed. FDS-RII is a relational storage system, designed to accelerate relational algebraic operations which uses a hash-based algorithm to process relational operations. In the has-based algorithm, a relation is first partitioned into several clusters by a split function. Each cluster is then staged onto the main memory and further, a hash function is applied to each cluster to perform a relational operation. Thus, the nonuniformity of split and hash functions is considered to result from a nonuniform data distribution on the hash-based algorithm. It is possible to attenuate the effect of the hash function nonuniformity by increasing the number of processors and processing the buckets in parallel. In order to address the nonuniformity of split function, the combined hash algorithm is introduced. This algorithm combines the grace hash algorithm with the nested loop algorithm in order to handle the overflown bucket efficiently. Using the combined hash algorithm, it is found that the execution time of the nonuniform data distribution is almost equal to that of the uniform data distribution