Matthias F. Brandstetter wrote:
Hi all,
I have to plan and setup a mail solution for about 50.000 users, here are
some key features requested by our customer:
- self coded webfrontend w/ webmail and administration (filter, alias etc)
- 100MB quota per user
- autoresponder
- about 50.000 user
- online backup of data
- some more featuers for web frontend
Since I happily use qmail for some other (but smaller) installations, I
want to try it with qmail here for this project as well. My only problem
is, I have no clue where to start ... beginning from should I use 2
redundant and really strong or some more but cheaper servers? to which
qmail distributions and patches should I use (ldap, mysql, ...)? and how
to store data (mails) and do online backup w/o downtime?.
I know you can't give me _the_ solution for this issue, but I am thankful
for any hints and internet links on this topic.
I'd go with three or more servers if possible. That way doing
maintenance is easy and losing a server due to failure is annoying, not
an emergency. I like my sleep.
Mail tends to be I/O intensive, again depending on a number of factors,
so having more cheaper machines is an easy way to get more I/O. On the
other hand, spam filter can be CPU intensive and use a ton of RAM.
Unfortunately my exp has been at the wrong ends of the scale. Previous
job was 5 million active mail boxes and the current gig is barely
pushing 1000. The large system had numerous cluster that supported mail.
The pop cluster, smtp-relay, smtp-inbound, spam/content filtering, imap,
http-frontend so it was easy to fix miscalculation in usage by throwing
more hardware at the problem.
If you support webmail you need an imap backend. The squirrel mail site
has a lot of good info about picking your imap backend and lots of
general performance data. I'd lean towards Courier-imap as it's probably
the fasted IMAP server that doesn't use it's own data format.
I'd look around and see what you can modify to your own use rather than
create from scratch. Squirrel mail, horde, postfixadmin, etc are all
packages that do some of what you want. Unless you've got a lot of time
and people to develop and know that you're never going to allow your
packages to face the public Internet then it might be doable.
In an environment your size I assume you're looking at shared storage
via NFS or something similar. A number of places have had good luck with
Netapp, but it's pricey. You might want to look at some of the cheap
Dell stuff which is rebranded EMC.
Maildir format is probably best for using shared storage, but things
can get interesting have a few million files on your filesystem. With
50k users you shouldn't see any of the stranger issues, but you may want
to keep an eye on inode usage. Reiserfs may be your best bet here.
I use Mysql on my current system with Postfix. I assume qmail can play
nicely with Mysql as well. I am running into some Mysql connection
problems because each Postfix process has it's own Mysql connection.
IIRC you can configure Mysql:proxy in Postfix and Courier to multiplex
queries over a single connection... something I'm planning on doing
later this month.
I used the qmail-1.03-r10 ebuild in production last time, but cut a
number of patches out since it was only for sending client emails to
customers. You'll probably want r15 since you're going to have users
directly connecting. Don't be afraid to cut patches you don't need, but
you'll definitely want to keep these big-todo and big-concurrency for
performance. qmail-link-sync support async filesystems, aka anything
journaled. The rest should be pretty self explanatory.
That's off the top of my head... hopefully it highlighted some issues
that you might have missed.
kashani
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