IAMP servers in FreeBSD for ISP

[Freddie Cash]

On Thu, July 6, 2006 7:52 pm, Francisco Reyes wrote:
> Anyone care to share what IMAP servers they have found to scale best?
>
>
> We are currently using courier and at times it seems it really will
> not scale well into thousands of emails.
>
> We have basically one setup with self contained machines that do all
> the work and a second setup where we break the load into MX machines,
>  NFS to store the maildir for courier and front end machines to run
> courier and NFS.
>
> We can handle hundreds of accounts in the self contained, more or
> less ok (depending on the mix of pop or imap).
>
> The second setup is more complex to meassure since the load is
> distributed. The biggest problem with this second setup is that the
> front end machines end up needing to mount several of the Maildir NFS
>  servers and we have found that one of the NFS servers going down can
>  affect all of the front end machines.
>
> What have others found to scale well and what kind of hardware are
> you using?

We used to use Courier IMAP, but then we found that it didn't handle
directories with more than 15,000 messages too well.  Especially with
lots of threads in there.

We moved to Cyrus IMAP, and haven't had issues since.  Some of our
users have 1.5 GB message stores, others are pushing 25,000 messages
in single folders.  We currently have less than 100 users on the mail
server, but we hope to move over all 1600 from the other three servers
they are currently on.  The really nice thing about Cyrus is that you
can cluster mail servers using the MURDER protocol to get a single
unified account namespace across distributed systems.  Sounds very
cool, and gives you an upgrade path (just add servers as needed).

Our IMAP server is currently running 64-bit Debian testing, Postfix,
Cyrus IMAP, IMAP Proxy, Apache2, PHP, and SquirrelMail.  Hardware is a
Tyan K8SD-Pro (S2882) motherboard, 4 GB ECC DDR-SDRAM, 3Ware Escalade
9550SX 4-port RAID controller, 4x 150 GB SATA HD in RAID5, Broadcom
Tygon3 GigE NIC.  We initially had issues with Apache hogging all the
RAM, but after tuning things we haven't had any issues.  Don't expect
we'll have issues until all 1600 accounts are on there, and then we
can start moving services off to other servers (move SquirrelMail to a
separate box, add IMAP servers using MURDER, etc).

----
Freddie Cash
fcash at ocis.net