IMAP Performance (again)

[karlp at ourldsfamily.com]

> 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


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