Monthly Archives: March 2014

Bloating Your Buffers

There’s one thing that has always bugged me when I review configuration files. People always seem to want to set certain buffer settings to ridiculously high values without really understanding what they’re doing.

Case in point: sort_buffer_size.

The misconception seems to be that setting this value to a high number will always improve a servers performance because everything works better with more memory, right? For some variables (key_buffer, innodb_buffer_pool) maybe, but the entire length of a sort buffer is allocated when ORDER BY is used. In practice, I find it best to leave it at default and watch sort_merge_passes in your status counter to determine if you need to adjust this value. Also, adjust in small amounts.


Capturing MySQL Data with tcpdump

Percona Toolkit has a great tool, pt-query-digest, that can use tcpdump data. Capturing raw tcp data can be taxing on a server, however, when you see the following message:

64000 packets received by filter
12000 packets dropped by kernel

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