[Dovecot] Big sites using Dovecot

[Joshua Goodall]

On Thu, Sep 21, 2006 at 06:14:14PM +0100, Jonathan wrote:
> Are there any big Dovecot sites (say 50,000-100,000) users on this
> list?

Yes. Actually, more users than that.

> What sort of hardware do you use.

2 x NetApp FAS2070c clustered filer heads w/NFS (fast fibrechannel
disk shelves)
IBM x336 SMTP/POP3/IMAP front-ends, 4GB RAM, 2x3GHz CPU.
Load-balancing across front-ends via Cisco 6509 SLB.
Gigabit Ethernet, jumbo frames.

> What sort of problems do you see?

You need a stable NFS client.  We're using Linux 2.6.16 with
NFS client patches from Trond Myklebust.

nfs mount options:
10.x.x.x:/vol/mailstore /var/mailstore nfs rw,tcp,nfsvers=3,rsize=8192,wsize=8192,nosuid,nodev,soft,intr,noac,actimeo=0 0 0
 
dovecot.conf
-  mmap_disable=yes
-  lock_method=fnctl

It's extremely fast & stable (server loads rarely above 1.0), serving
a six-figure userbase their spam, their mailbombs, and just
occasionally, some genuine mail :)

Other major platform components: OpenLDAP 2.3, Postfix 2.3.

The main bottleneck is Postfix spooling before delivery, but I have
to generate synthetic mailbombs to make it seriously blink (and I'm
still in the "Dovecot probably needs a LMTP speaker someday" camp).
We can eliminate even that with /var/spool/postfix on a tmpfs, but
I'm unwilling to go that far.

Note: without Trond M's NFS client patchset we see comedy VFS
out-of-sync errors after a few days uptime, resulting in mistaken
deadlocking of dovecot indices (usually only one user, but always
a high-volume user) that needs a node reboot to fix, and some
intervention with the "lock status / break" command on the OnTAP
command line. With the patches it's been rock solid.

If only I could make anti-spam services run so fast! Timo, could
you design a mail hygiene system next? Thanks :)

all the best
JG

-- 
Josh "Koshua" Goodall                      "as modern as tomorrow afternoon"
joshua at roughtrade.net                                       - FW109