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@roughtrade.net - FW109