IMAP Wildlife problems ....

[Bill Campbell]

On Thu, Oct 12, 2006, Ben Duncan wrote:
>No, not that kinda wildlife. This involves one of my clients,
>the MS Department of Wildlife Fisheries and Parks.
>
>We are having IMAP services bringing their Mail server to
>it's knees.
>
>Server: Dell Dual Xenon 3.2 Rack mount server with 4GB main
>memory , dual 1000 ethernet NICS, and close to 1TB of SCSI
>320 RAID.
>
>OS: Slack 10.2 with kernel 2.6.18 Sendmail version that was
>the most recent as of March of this year along with
>UW's Imap4Rev1. We use IMAP only as the server and no POP.
>
>We have about 1200 subscribers and the breakdown is thus:
>60% of the users have 15Mb and less in their inbox.
>20% Of the users have 15Mb+ - 100Mb in their inbox
>10% of the users have 100Mb+ - 400Mb in their inbox
>5%  of the users have 400Mb+ - 1GB in their inbox
>5%  of the users have 1GB+ in their inbox.
>
>Seems everyone in the LARGE (100Mb+) inbox likes having
>their MS OUTHOUSE check the inbox every 30 or so seconds. This seems
>to be killing the machine.
>
>Anyway, we are thinking about switching from UW Imap and maybe
>going to Cyrus (or maybe even Courier / DoveCot).

We have been using courier-imap for about five years now, and
have been very happy with it.  Its use of standard Maildir mail
stores has allowed us to set up clusters of servers at busy ISPs
to spread the load of incoming mail processing with postfix and
POP3/IMAP across multiple servers.

Courier also maintains a pool of servers listening for POP3 and
IMAP connections, much as Apache does which eliminates the
startup time and rate problems associated witn (x)inetd started
server processes.

Using Maildir allows one to use standard *NIX tools to do things
like purge old messages, grep messages for patterns, etc. without
having to worry about dealing with the Cyrus specific files.

Cyrus uses a somewhat different mail store, while keeping
messages in individual files as Maildir does, it maintains a
central database and indexing structure which can cause problems.

FWIW:  I have written a script that converts from UW IMAP's
binary single file MBX format to Maildir, and I suppose others
have done similar things.

Bill
--
INTERNET:   bill at Celestial.COM  Bill Campbell; Celestial Systems, Inc.
UUCP:               camco!bill  PO Box 820; 6641 E. Mercer Way
FAX:            (206) 232-9186  Mercer Island, WA 98040-0820; (206) 236-1676
URL: http://www.celestial.com/

``Rightful liberty is unobstructed action according to our will within
limits drawn around us by the equal rights of others. I do not add 'within
the limits of the law' because law is often but the tyrant's will, and
always so when it violates the rights of the individual.''
    -Thomas Jefferson