holland-coredev team mailing list archive

[Andrew Garner <muzazzi@xxxxxxxxx>]

I pushed a tentative change to holland-backup/master earlier this week
to improve purge backups on ext3.   This does a gradual ftruncate() on
files before doing an unlink().   This was done to address some
performance issues when holland has large files (particularly large
tarballs) in $backup_directory and simply unlink()ing those on ext3
causes a huge io spike and often io stalls, particularly if something
like mysql, happens to be doing synchronous io on the same filesystem.

This is essentially the same issue discussed here:

http://www.mysqlperformanceblog.com/2009/06/16/slow-drop-table/

Although not directly related to MySQL in this case. :)   XFS
significantly improves this but you can still see stalls of a few
seconds (but much less dramatic than the 2+ minutes of ext3), so I
think the approach is generally useful in unix environments.

This change came in here:

https://github.com/holland-backup/holland/commit/8010ab72525e1be02f14c4f39a1f06083fb3d425

I am throwing it out here in case anyone has any comments or concerns
with this approach.

~Andy