[Dovecot] Dovecot + DRBD/GFS mailstore

[Eric Jon Rostetter]

Quoting Guy <wyldfury at gmail.com>:

> I'm looking at the possibility of running a pair of servers with
> Dovecot LDA/imap/pop3 using internal drives with DRBD and GFS (or
> other clustered FS) for the mail storage and ext3 for the root drive.

I'm in testing right now with this setup.  Two Dell PE 2900 servers
(quad core @ 2.3 GHz, 8 GB RAM, raid 10 for the GFS+DRBD disk, raid 1
for the ext3 disks).  Running DRBD as a master/master setup.

I added a third node for webmail (Dell PE 2650), but it doesn't do the
DRBD or GFS.  It is there mostly to make a 3-node cluster versus 2-node
cluster, to avoid split-brain type situations.  And of course to do the
webmail. :)

Using MailScanner as the MTA, dovecot for pop/imap, mailman for mailing
lists, Horde/IMP/etc for webmail.   All held together with RHCS on CentOS
5.3.

All services run on only one node at a time, with failover...  This may
or may not help with GFS lock contention (not for /var/spool/mail, since
it is always accessed from both nodes at once, but yes for dovecot indexes
since they are only ever accessed on one node at a time, etc).  This is
probably where performance will really be decided (GFS lock contention).

Cluster Status for mailer @ Mon Aug 24 10:27:12 2009
Member Status: Quorate

  Member Name                             ID   Status
  ------ ----                             ---- ------
  mailer1-hb.localdomain                      1 Online, rgmanager
  mailer2-hb.localdomain                      2 Online, Local, rgmanager
  webmail1-hb.localdomain                     3 Online, rgmanager

  Service Name                   Owner (Last)                   State
  ------- ----                   ----- ------                   -----
  service:Apache                 mailer1-hb.localdomain         started
  service:Dovecot                mailer1-hb.localdomain         started
  service:MailMan                mailer2-hb.localdomain         started
  service:MailScanner            mailer2-hb.localdomain         started
  service:VIP-MAIL               mailer1-hb.localdomain         started
  service:VIP-SMTP               mailer2-hb.localdomain         started
  service:WebMail                webmail1-hb.localdomain        started

> Has anyone had experience with a setup like the one I'm suggesting?
> What was performance like with Dovecot using GFS?

So far it is early testing.  63 users, but only about 12 of those are
"power users".  The performance has been real good so far, but as I say,
not many users yet.

My GFS is sharing the mail log files (via syslog-ng, what would otherwise
be /var/log/maillog), the dovecot index files, the /var/spool/mail/ mbox
spool (yes, I use mbox), and "shared" configuration files for the two nodes
(mailman data, MailScanner/Sendmail configs, dovecot config, clamav/spamd
config, procmail config, apache config, ssl certificates, etc).

If interested, I can let you know about performance once I know more...

> Thanks
> Guy

-- 
Eric Rostetter
The Department of Physics
The University of Texas at Austin

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