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Re: Qmail or Zmailer



In message <19990202224455Z2911-2277+4112@nic.funet.fi>you write:
>We are looking to build a high performance mail-cluster for pop3, imap4 and
>smtp. The system uses an LDAP database to validate and deliver the users mail.
>
>The system needs to scale to around 500,000 users - the questions I have:
>
>1. Which is better for this Qmail or ZMailer

It should be possible to use either one.   ZMailer is complex and powerful.
Qmail is, I think, a little simpler and quicker.  Both are probably
sufficiently quick on modern hardware.

>2. What would be the best way of creating a high availability service -
>multiple POP3, multiple SMTP, etc pointing to common NFS mount?

It'd be better to avoid NFS altogether if possible.  Locking over NFS is slow
and not always robust.

>3. Has anyone found any major issues with Zmailer which stop it scaling.

The first bottleneck you're likely to see is disk I/O in the postoffice 
directory, since zmailer does a lot of reading and writing in that directory
as messages get passed from one program to another.   Fast disks help.
Battery-backed write caching also helps.  You might try a RAID controller
with such caching built in, e.g. CMD 5500.

Regards,

John
--
John DiMarco <jdd@cs.toronto.edu>                         Office: SF2101
CSLab Systems Manager                                     Phone: 416-978-5300
University of Toronto                                     Fax:   416-978-1931
http://www.cs.toronto.edu/~jdd