[CentOS] atime, relatime query

nate centos at linuxpowered.net
Wed Feb 3 22:33:34 UTC 2010


Rob Kampen wrote:

> I do not agree - every read of the db will update the filesystem with
> noatime missing, thus specifying noatime does give performance
> improvements - the size of the files does not matter as much - rather
> the number of reads vs writes.

Interesting, didn't think about that aspect, I dug around and at least
for MySQL and Postgresql noatime doesn't appear to provide any
noticeable benefit(it may be a measurable one in some cases)

http://www.mysqlperformanceblog.com/2007/11/01/innodb-performance-optimization-basics/

http://www.ffnn.nl/pages/articles/linux/server-wide-performance-benchmarking.php

If your doing a ton of reads and only have a few files, it's likely
there isn't going to be many atime updates as the file is kept open
for an extended period of time(e.g. scanning a table with 100k rows).

For DB performance there's a lot more useful areas to spend time
tuning. As DBAs often say you can get 10% more performance tuning
the OS and getting better hardware, and you can get 1000% better
performance by tuning the queries and data structures, or something
like that :)


nate




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