On Wed, 28 Jun 2006, Aaron W. LaFramboise wrote:
To Andrew:
I can confirm Mark's comments that there is something probably wrong
with your benchmark. I have done this test on a similar Linux system
(although not the same benchmark), and got pretty much the opposite
result as you, with or without disk caching effects.
Looking at the URLs you mentioned, I see an exceptionally high Error
count for mbx (3,873,234,974) compared to mbox (10). Perhaps this is
the source of the problem?
This mail has been sitting in my drafts folder (OK, Pine "postponed")
since before I went on vacation.
I changed my approach, and scripted a lot of tests with 10-20 clients and
running for about a minute. I preloaded accounts with about 5000 messages
in a mix of sizes, added a bunch of "recent" mails and started the Bonnie
IMAP client. However, it still doesn't behave like a human. It certainly
doesn't behave like me - I read mail in a random order, reading some,
deleting others unread etc. while remaining logged on for hours. So if it
seems to be saying that mbox on XFS is fastest, I'm not sure I believe
it. I also find a discrepancy between messages retrieved (try/sec) and
bytes retrieved.
.. if I look at the "transfer time" graphs, the Mix format seems to
show more consistent times and be quicker to get an individual message.
But that doesn't show in the summary pages.
The powers that be want me to get on and upgrade the mailserver before it
melts and stop messing around, so I probably won't spend too much more
time on this. I'll probably toss a coin and choose, say, XFS and Mix,
which gives me back-compatability with existing files and gets away from
huge inboxes with their subsequent backup problems.
http://andrew.triumf.ca/linfs/mstone.html
Back in July, I started to write:
What benchmark software did you use ?
Have you looked at Maildir format (e.g. Courier) ? It looks similar to
mix, though AFAIK some metadata is coded into the filename rather than
stored in separate files, and it sounds like mix has more capability.
I notice that RHEL4 now includes Dovecot and Cyrus imapd, not UW. As far
as I can tell, though Dovecot supports Maildir format, a delivery agent
is not included in RHEL (or I didn't find it). I built Courier maildrop
which worked for me. Cyrus I have not yet tried. (mail delivery and how
to create an inbox seems different for everything, and moreso for Cyrus)
I have seen comments that Dovecot imapd outperforms UW imapd through
better memory management, though this is not obvious in mailstone. Maybe
the comment applied to an earlier version.
I've also seen comments, which I do seem to verify, that a filesystem
such as XFS or Reiser is better suited to Maildir/mix structure than
"traditional" ext2/3. (I've had in-house comments about stability
problems with Reiser on SL4 (~= RHEL4)). I see XFS being somewhat
better, cf. ext2, ext3, Reiser 3.4, and JFS.
Andrew
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