tailieunhanh - Parallel Database Systems: The Future of High Performance Database Processing

Despite evidence to the contrary, chemical industry critics of epidemiologic studies linking pesticides to major diseases argue that they are of limited value because of their reliance on records and study participants’ memory, among other issues. In fact, the correlation of patterns of chemical use with an effect is difficult to establish in epidemiology and therefore may underestimate hazard effects. When a correlation is established it raises serious concern. The epidemiologic studies in the Pesticide-Induced Diseases Database show an overall pattern that links pesticide exposure to major diseases. Inherent limitations, such as the following, only add to the power of. | Parallel Database Systems The Future of High Performance Database Processing1 David J. DeWitt2 Computer Sciences Department University of Wisconsin 1210 W. Dayton St. Madison WI. 53706 dewitt @ Jim Gray San Francisco Systems Center Digital Equipment Corporation 455 Market St. 7 th floor San Francisco CA. 94105-2403 Gray @ January 1992 Abstract Parallel database machine architectures have evolved from the use of exotic hardware to a software parallel dataflow architecture based on conventional shared-nothing hardware. These new designs provide impressive speedup and scaleup when processing relational database queries. This paper reviews the techniques used by such systems and surveys current commercial and research systems. 1. Introduction Highly parallel database systems are beginning to displace traditional mainframe computers for the largest database and transaction processing tasks. The success of these systems refutes a 1983 paper predicting the demise of database machines BORA83 . Ten years ago the future of highly-parallel database machines seemed gloomy even to their staunchest advocates. Most database machine research had focused on specialized often trendy hardware such as CCD memories bubble memories head-per-track disks and optical disks. None of these technologies fulfilled their promises so there was a sense that conventional cpus electronic RAM and moving-head magnetic disks would dominate the scene for many years to come. At that time disk throughput was predicted to double while processor speeds were predicted to increase by much larger factors. Consequently critics predicted that multi-processor systems would soon be I O limited unless a solution to the I O bottleneck were found. While these predictions were fairly accurate about the future of hardware the critics were certainly wrong about the overall future of parallel database systems. Over the last decade Teradata Tandem and a host of startup companies have .