Greg,
I concur with the others who've replied to this message - there's
no reason you can't run the size of userbase you propose on
Qmail - two of the installations I've worked with are already happy
at the half-a-million-users mark and should scale into the millions
(these run on Solaris and Linux).
The 'Classical' solution for a large installation of Qmail revolves
around NetApps, a solution that has worked very well for me - this
offers an effective FS, RAID, and nice rollback (snapshot)
functions, maximising the data-integrity of users E-mail. Also, since
NetApps have a good chunk of battery-backed memory, they can
'Sync' faster than a normal hard disk (once the NetApp says it's
written a file, you can trust it to make sure it'll do so).
The advantage with a NetApp - or probably any SAN - is that
you can have multiple qmail front-ends to it, rather than having to
buy the biggest machine you can lay your hands on (which will
still - as you are finding - have limitations in terms of the hard
disks).
With Solaris, Veritas do a journalling-style filesystem, which will
offer improved performance over UFS. Also ensure that you don't
have any huge directories: many Unix filesystems struggle with large
directories, so think about using hashing to distribute your
files (user dirs etc.) into manageably-sized directories.
It would seem Sun aren't being very imaginative with their Qmail
figures, perhaps for the reason Toens mentions... but I'd suggest
that it is necessary to have a careful Qmail design for it to scale
properly anyway (My technique, when I first had to design a
large system like this as a Qmail-newbie was to get some
consultancy from Russ Nelson: Consultancy is cheap compared
to anything you buy from Sun... ;-)
cheers,
Andrew.
----------
From: Toens Bueker[SMTP:[EMAIL PROTECTED]]
Sent: 28 June 2000 15:31
To: [EMAIL PROTECTED]
Subject: Re: Building very large Qmail instalations...
Greg Moeller <[EMAIL PROTECTED]> wrote:
> I'm one of the admins of a largish Qmail installation (~60,000 mailboxes)
> and the hardware we're running it on it near the limit.
> (Sun Ultra 450, dual processor, A1000 storage array)
> The system is very IO bound, sometimes with a load average of 20-25.
> (although usually between 3-8)
>
> Now, we called Sun, asking about a high capacity disk solution, one that might
> help with the IO problems. (cache on the disk array to take care of all the
> fsyncs Qmail does) They told us that around 50k-60k
> mailboxes is about the limit of Qmail.
>
> Now, my question to all of you is how expandable is Qmail, and what's the best
> way to do it?
>
> We're looking to expand the system to 150,000-200,000 mailboxes.
Their answer was predictable - at least they have to try
and sell their SIMS.
I don't know about qmail - but as we have used a Sun U2
(two cpus) with 100,000 mailboxes for a short period of
time with sendmail, qmail should easily handle much more.
The problem - in this case - is Suns filesystem and qmails
file operations. You didn't mention the number of disks in
your A1000 - but maybe you should add some and spread the
load between them.
My suggestion, though, would be to dump the E450 and grab
a reasonable sized Intel box (maybe dual PII 500) with FreeBSD
on it. With FreeBSD, ffs and softupdates your i/o
headaches should be gone.
By
T�ns
--
Linux. The dot in /.
