slow IMAP data transfer
mloftis at wgops.com
Thu Feb 9 16:21:01 EST 2006
--On February 9, 2006 10:46:29 AM +0000 David Carter <dpc22 at cam.ac.uk>
> Cyrus and Postfix both make very heavy use of fsync() to flush data to
> disk before they confirm actions back to the sending system. RAID
> controllers or disk boxes with battery backed writeback cache help lots.
I'll confirm what David and Henrique both posted. Cyrus, postfix, and
friends, make a LOT of use of fsync. This will cause a lot of I/O, esp if
your RAID doesn't have a write cache. I'd also suggest only using a
battery backed write cache.
We see similar behavior on Linux with Cyrus, Postfix, and MailScanner (also
running SpamAssassin). If/when we get into a situation where our AX100 or
CX200 disable their write caches the mailserver usually pretty much pukes
since it's constantly causing sync's.
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