This paper extends earlier research on hash-join algorithms to a multiprocessor architecture. Implementations of a number of centralized join algorithms are described and measured. Evaluation of these algorithms served to verify earlier analytical results. In addition, they demonstrate that bit vector filtering provides dramatic improvement in the performance of all algorithms including the sort merge join algorithm. Multiprocessor configurations of the centralized Grace and Hybrid hash-join algorithms are also presented. Both algorithms are shown to provide linear increases in throughput with corresponding increases in processor and disk resources. 1.

This thesis proposes ideas for designing file system software for large, high-performance file server hardware we feel will be common in the middle to late nineties. In particular, the thesis examines the value and pragmatics of file systems with multiple file implementations. A file implementation determines how a file is represented in secondary storage and the procedures by which that representation is interpreted. A file system with multiple file implementations can use different implementations for different files. The thesis also proposes an allocation algorithm designed for a system with device parallelism and multiple file implementations, and it reports the results of a trace-driven simulation study evaluating the algorithm. The thesis proposes parameterizing file behavior to give users control over which implementation is used for a file without exposing the low-level details of implementations.

This thesis looks at various issues in providing application-level software support for parallel I/O. We show that the performance of the parallel I/O system varies greatly as a function of data distributions. We present runtime I/O primitives for parallel languages which allow the user to obtain a consistent performance over a wide range of data distributions. In order to design these primitives, we study various parameters used in the design of a parallel file system. We evaluate the performance of Touchstone Delta Concurrent File System and study the effect of parameters like number of processors, number of disks, file size on the system performance. We compute the I/O costs for common data distributions. We propose an alternative strategy-two phase data access strategy- to optimize the I/O costs connected with data distributions. We implement runtime primitives using the two-phase access strategy and show that using these primitives not only I/O access rates are improved but also ...