[Dovecot] Migration questions...

[Richard Hobbs]

Hi All,

We are soon to migrate our mail server from one piece of hardware to
another and we would like to take this opportunity to optimize things.
As a result, we would like to replace "uw-imapd" and "qpopper" with
"dovecot". The version we will be installing is 1.1.13-2, as this is
what is available through the latest Debian stable backports. We will
also be using exim to deliver mail (through dovecot's deliver mechanism,
of course).

So... We are currently using the mbox format with uw-imapd, and would
like to migrate to the fastest solution possible with dovecot on the new
hardware. My understanding is that "multi-dbox" is not an option in this
version anyway, maildir is OK, but not great, and "single-dbox" is
therefore going to be the highest performing solution. Is single-dbox
the fastest way to go, considering we're going to be using email in the
following ways:

 - IMAP connections with all email in the Inbox (Gmail-style).
 - IMAP connections with email split into many IMAP folders.
 - POP3 connections with no email left on the server.
 - POP3 connections with *all* email left on the server.

All connections check for new mail every 5 minutes (on average) and
there are 50-60 users). Also, we are not able to change user behaviour
in this instance, unfortunately.

Can anyone see any problems with the above proposal? Hopefully not...

One problem that may arise is the fact that when we migrate, all msg
UIDs will be lost. If i'm not mistaken, this means that all emails will
be treated by the mail client as brand new, and if through IMAP, will
all go bold, and if through POP3, will all be downloaded again (if still
on the server) and therefore duplicated in the mail client. If this is
the case, is there anything we can do to stop this happening? Does the
"Convert" plugin does this job well?

Finally, I have a rough draft of our migration plan - is there anything
horribly wrong in it that's going to cause lots of problems, that anyone
can spot by any chance?

1. Install Debian with exim, mysqld (for Horde/IMP) and mailman.

2. Run an online update.

3. Rsync homedirs and inboxes onto new server, ready for initial exim
configuration.

4. Configure exim as per existing mail server and test that mailing
lists and normal email works.
   You should now have the existing mail delivery solution on the brand
new hardware.

5. Once mail delivery is sorted, add "deb
http://www.backports.org/debian lenny-backports main contrib non-free"
into "/etc/apt/sources.list" and run "aptitude update && aptitude
install debian-backports-keyring && aptitude update".

6. Install dovecot (at the time of writing, this was version 1.1.13-2)
and configure to use existing mbox files (inboxes in /var/spool/mail/
and IMAP folders in /home/user/mail/)

7. Setup exim to use dovecot's "deliver" mechanism for interacting with
the inboxes (which are still in mbox format).

8. Configure the "convert" plugin to begin converting the mail to dbox
format.

9. Run something manually (if possible) to convert mailboxes before
people connect, so the task is already done by the time the outage is over.

10. Give staff access to new speedy mail server!

Thanks in advance, people - any help is greatly appreciated! :-)

Richard.

-- 
Richard Hobbs (IT Specialist)
Toshiba Research Europe Ltd. - Cambridge Research Laboratory
Email: richard.hobbs at crl.toshiba.co.uk
Web: http://www.toshiba-europe.com/research/
Tel: +44 1223 436999        Mobile: +44 7811 803377
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/x-pkcs7-signature
Size: 3306 bytes
Desc: S/MIME Cryptographic Signature
Url : http://dovecot.org/pipermail/dovecot/attachments/20090511/c36273fa/attachment-0001.bin