5.1 Optimisation Overview

The most important part for getting a system fast is of course the basic design. You also need to know what kinds of things your system will be doing, and what your bottlenecks are.

The most common bottlenecks are:

• Disk seeks. It takes time for the disk to find a piece of data. With modern disks in 1999, the mean time for this is usually lower than 10ms, so we can in theory do about 100 seeks a second. This time improves slowly with new disks and is very hard to optimise for a single table. The way to optimise this is to spread the data on more than one disk.
• Disk reading/writing. When the disk is at the correct position we need to read the data. With modern disks in 1999, one disk delivers something like 10-20 MB. This is easier to optimise than seeks because you can read in parallel from multiple disks.
• CPU cycles. When we have the data in main memory (or if it already were there) we need to process it to get to our result. Having small tables compared to the memory is the most common limiting factor. But then, with small tables speed is usually not the problem.
• Memory bandwidth. When the CPU needs more data than can fit in the CPU cache the main memory bandwidth becomes a bottleneck. This is an uncommon bottleneck for most systems, but one should be aware of it.

Subsections

• 5.1.1 MySQL Design Limitations/Tradeoffs
• 5.1.2 Portability
• 5.1.3 What Have We Used MySQL For?
• 5.1.4 The MySQL Benchmark Suite
• 5.1.5 Using Your Own Benchmarks

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