On Thu, Aug 21, 2008 at 11:38:56AM -0700, Gregory K. Ruiz-Ade spake thusly:
> So I'm not the only one this happens to...

This document seems to have a pretty good explanation of the cache and
pdflush behavior:

http://www.westnet.com/~gsmith/content/linux-pdflush.htm

"The usual issue that people who are writing heavily encouter is that
Linux buffers too much information at once, in its attempt to improve
efficiency. This is particularly troublesome for operations that require
synchronizing the filesystem using system calls like fsync. If there is a
lot of data in the buffer cace when this call is made, the system can
freeze for quite some time to process the sync."

You may be doing more writing than you realize. Also realize that disk is
just really slow. You can look at /proc/meminfo as suggested in the above
document to see how much in the way of outstanding writes you really have.
Putting a sync in crontab should not be necessary.

-- 
Tracy Reed
http://tracyreed.org


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