[Dovecot] Re: Dovecot stable slow

[Loren M. Lang]

On Sun, Jun 12, 2005 at 09:09:55AM +0200, Quest wrote:
> "Loren M. Lang" <lorenl at alzatex.com> writes:
> 
> > A few days ago I installed dovecot stable to replace uw-imap. The
> > install went well and all boxes were converted ok. When accessing
> > the new imap server though, certain operations seem much slower, in
> > particular, moving mail between boxes is very slow, and I have
> > received several complaints from users that the mail server has
> > slowed down. I can't figure out what the slow point is as maildir
> > should be faster than mbox.
> 
> What UNIX are you running on, what filesystem and what kind of
> hardware are we talking about? Is maildir_copy_with_hardlinks set?

Linux 2.4 kernel on redhat 9 using reiserfs on all partitions with raid1
on 2 100 gig 7200 rpm wd drives.  P4 2.4G  800Mhz FSB w/HT but HT has
been recently turned off do to the vulnerability in it.  Also 1G DDR
2700 ram.  It's pretty close to the example config file so that option
is turned off.  I could try enabling it, but I am currently running
0.99.x, with it's own default config modified slightly, but it that
option is still disabled and runs just fine so I don't think that is the
slow part.  Some difference between stable and 0.99.x seems to cause the
slowdown.  I could compare the two config files, but I think it's a
difference in implementation rather than a different configuration.

> 
> I find that there are circumstances on modern hardware when mbox is
> actually faster than maildir. An Intel box with a good disk system
> will easily load and traverse a multi-megabyte mbox in the time it
> takes to do a few seeks on the disk (ie finding the various mails in a
> maildir).

I'd still expect maildir to beat mbox in modifying/deleting specific emails
in a large (2000+) email box, but I can see how searching or downloading
could be faster using mbox.

> 
> Of course, on dovecot, you can't have folders in folders with mbox, so
> it's not really an alternativefor me. But maybe you should try it to
> compare. If your users mostly do operations on massive amounts of
> mail, it may be an improvement on modern hardware.

I may try this, but as this is a live mail server, I can only do limited
testing.

> -- 
> Anders "Quest" Qvist
> 
> Ye olde jungle proverb:
> Even the Phantom must turn on the light to see what's in his goth wardrobe.
> 

-- 
I sense much NT in you.
NT leads to Bluescreen.
Bluescreen leads to downtime.
Downtime leads to suffering.
NT is the path to the darkside.
Powerful Unix is.

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