A
A Simple Performance Model for Databases
Performance is your reality. Forget everything else.
—Harold Geneen
This appendix presents a simple performance cost model for evaluating physical design methods and tradeoffs among various designs. The model includes estimations for input/output (I/O) time and network delays.
A.1 I/O Time Cost—Individual Block Access
A block (or page) has been traditionally the basic unit of I/O from disk to fast memory (RAM). It can range in size from 2 to 16 KB, although 4,096 bytes (4 KB) is the most typical size in many systems. Blocks usually include many rows in a table, but occasionally a large row can span several blocks. In recent years, prefetch buffers have been used more often in operational systems to ...
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