IMAP Performance (again)

[Bob McClure Jr]

On Wed, Aug 24, 2005 at 08:10:50AM -0600, karlp at ourldsfamily.com wrote:
> > On Tue, Aug 23, 2005 at 03:27:52PM -0600, karlp at ourldsfamily.com wrote:
> >
> >> BUT, I have figured something out. Whenever an Outlook Express IMAP user
> >> accesses the server, it's unbearably overwhelming to the system and
> >> causes
> >> incredible slowness. When Pine or Squirrelmail users access the system,
> >> there's no noticable performance hits. With Pine, I understand because
> >> it
> >> doesn't access all the folders everytime it tries to update things.
> >> Outlook Express does this, as does Squirrelmail if the option is set.
> >> With
> >> the option set in Squirrelmail, it doesn't hit the server as hard as
> >> Outlook. Or, have I been smoking something? (don't answer that)...
> >
> > In my experience, we had extreme performance slowdowns when using the
> > UWash imapd.  What was happening is that the users had large spools
> > or folders, and since UWash was spawning a new instance every time
> > someone connected to it, nothing about the mailbox(es) was getting
> > cached; which meant that these large spools or folders had to be read
> > each and every time the folder was accessed.  Multiply this by
> > extreme email hoarding (people with a gig in their inbox spools were
> > not uncommon) and volume (over 150 people accessing the server) and
> > you had for a very large, very powerful computer doing nothing but
> > waiting on disk I/O.
> >
> > Our solution was to use the cyrus IMAPd.  This uses a different
> > format for storing email, but more importantly the message statuses
> > were stored in a database format separate from the actual messages,
> > which meant that folder status queries (ie, anything new in my
> > inbox?) were much lighter, more likely cached, and due to both
> > reasons, much faster.
> >
> > The learning curve for cyrus is much steeper than UWash (especially
> > if you are doing either virtual domaining and/or building from source
> > on Solaris); but in our case it was well worth it as it saved us the
> > cost of a brand new machine.
> 
> Wow, Great information! I guess the learning curve starts now. With 2 mail
> servers, this will help more than one community of users.
> 
> When I decided to install mplayer several years ago, I got a working copy
> going, including codecs, etc. and put the whole kit and kaboodle on a
> single CD. Doing that made my life easier as I moved up the upgrade path.
> . . I guess doing the same with Cyrus might be a good idea so disaster
> recovery can be done much easier.
> 
> Again, thanks.
> 
> Karl

Well, before you jump too quickly, you might check out dovecot.  It is
the default IMAP (and POP3) server in the Fedora Core set, replacing
the UW package.  I have no information on its technical virtures over
UW, if any, but it configures more simply than Cyrus.  I'm using it on
our local ISP's mail server which has over 1100 customers and is
_very_ busy.

Cheers,
-- 
Bob McClure, Jr.             Bobcat Open Systems, Inc.
robertmcclure at earthlink.net  http://www.bobcatos.com
Peace at any price is inflationary.