On Thu, 9 Jun 2011, Emmanuel Noobadmin wrote:
> I'm trying to resolve an I/O problem on a CentOS 5.6 server. The
> process basically scans through Maildirs, checking for space usage and
> quota. Because there are hundred odd user folders and several 10s of
> thousands of small files, this sends the I/O wait % way high. The
> server hits a very high load level and stops responding to other
> requests until the crawl is done.
If the server is reduced to a crawl, it's possible that you are hitting
the dirty_ratio limit due to writes and the server has entered synchronous
I/O mode. As others have mentioned, setting noatime could have a
significant effect, especially if there are many files and the server
doesn't have much memory. You can try increasing dirty_ratio to see if it
has an effect, eg:
# sysctl vm.dirty_ratio
# sysctl -w vm.dirty_ratio=50
Steve
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