Re: [exim] Exim Performance / Server Performance

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Autor: Brian Candler
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A: GamCo - Gawie Marais
CC: exim-users
Assumpte: Re: [exim] Exim Performance / Server Performance
On Thu, Apr 28, 2005 at 12:48:08PM +0200, GamCo - Gawie Marais wrote:
> !! >> We limit mailboxes to 10 megs. Hence that said, no mailbox should be
> larger that 10 megs as we reject mails coming in if it exceeds 10 megs.


A mailbox which contains 10 megs is still going to hit your disk hard for
several seconds every time a user opens it, since it has to be read from
start to end just to count the "From " lines which separate the messages.

*Know your userbase*. How many mailboxes do you have right now which are
over 1MB? How many are over 5MB?

> > >> We are running MySQL on a total separate server. Although the server is
> > taking some train if I look at the loads, none of mail is put on the queue
> > because Exim can't access the MySQL database.
>
> How do you know?
>
> !! >> we get error messages sent to the console when no connection can be
> made to the MySQL database.


That's not a good answer. An exim daemon (such as an SMTP receiver) is very
unlikely to put a message onto the console.

You need to look in your exim log files and look especially for lines which
contain the word 'defer'

> Or go for something more efficient. For example, you can get Exim to deliver
> in Maildir format, and then use courier-imap as the POP3 server. That's a
> major redesign in your system though.
>
>
>
> !! >> is it a major job and whats the implications changing from a mailbox
> to maildir delivery method -- perhaps I can read up on it somewhere ??


I wrote some notes at http://www.ws.afnog.org/afnog2004/t1/mail/courier.htm
but that website is currently off-line and may well be so for a few more
days.

If you want to go that route, I suggest you build yourself a new test
system. Get comfortable with the new pop3 daemon you'll be using. Make the
(minor) config changes to Exim to deliver into Maildir format. And then find
some scripts for converting mbox files to maildir, and practice performing
the conversion.

Regards,

Brian.