I've got a MySQL database (MyISAM) that handles a lot of read/writes and uses temporary tables quite frequently.

Recently it's started having massive load spikes at peak load, and noticed that there were a lot of temporary tables being written out to disk in the /tmp directory.

I've increased the key_buffer variable to 4GB (was 16MB) and tested performance with JMeter, but to my surprise, while the website seems slightly faster, JMeter data is reporting the change has increased response times by a 100's of milliseconds.

Is there something I'm missing or other variables I need to tune to stop MySQL writing tables to disk?

This server has 16GB RAM.

  • Find the slow queries. Provide us with SHOW CREATE TABLE and EXPLAIN SELECT... for them. – Rick James Jul 6 '15 at 21:17

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