DoveCot vs Cyrus-Imapd Performance

Ow Mun Heng Ow.Mun.Heng at
Sat Jan 15 07:28:29 UTC 2005

On Sat, 2005-01-15 at 05:38, Aleksandar Milivojevic wrote:
> Kevin Fries wrote:
> > Les Mikesell wrote:
> > | On Fri, 2005-01-14 at 00:00, Aleksandar Milivojevic wrote:
> > |
> > |
> > |>And exactly how scalable are user accounts (the ones stored in flat
> > file called
> > |>/etc/passwd)?  That will not scale well.
> > |
> > |
> > | I think you know that's irrelevant for anything using PAM.  Dovecot is
> > | equally capable.
> > 
> > I have a mail server that supports approximately 50-60 radio stations
> > across the country with approximately 700 end users.  Because of the
> > dispersant number of users and geographic locations, I have set up a
> > certain number of users at the main office to use Webmin to add accounts
> > to the mail server.  NOBODY is allowed shell access to the box but me,
> > and the Webmin limits these people's access to the add user applet.
> > 
> > Despite using system accounts which Aleksandar thinks is unscalable,
> > this setup works perfectly.  As new radio stations come online, we
> > create a simple text file and accounts are created in batch.  As each
> > account is crated, their mail box is set up.
> 700 users is nothing.  You will not see any problems with scalability 
> with that user base.  Multiply it by 100, and you'll start seening first 
> problems.  Go past 100,000, and things get preaty tight.

I agree. 700 is nothing. when we talk about using virtual users, we're
mostly talking about _large_ user bases. 

> Before my wife talked me into moving to Canada (and out of all the warm 
> places in Canada, Winnipeg was our destination), I've used to work for 
> large national ISP where user's were stored in actual /etc/passwd.  Mail 
> server worked well until user base got to about 50,000 users on 4-CPU 
> Alpha Server running Tru64 Unix (and later cluster of several Alpha 
> Servers).  Then, Internet boom hapened, and user base exploded.  Things 
> started to slow down drastically with each new user.  Local system 
> accounts proved not to be very scalable solution.  In those days, there 
> were no out-of-box solutions based on LDAP, like there are today.  So 
> what we did back than, we moved all users from shell accounts into 
> Oracle database, and made patches for sendmail, procmail, and qpopper to 
> work with users that exist only as records inside Oracle SQL database. 
> That same 4-CPU Alpha Server that was beginning to be painfully slow, 
> all the sudden was capable of hosting several milion mailboxes.  Now, 
> that is what I have in mind when I say scalability.
> If we were to do it again today, we'd probably simply use LDAP and 
> Cyrus, with little development time spent for transition.

You know.. How fast is LDAP compared to using SQL? For one thing, LDAP
is optimised for reads rather than writes.

I would believe that LDAP is more suitable in this case.

Writes are only needed when adding users and that doesn't happen as
often as reads.

Ow Mun Heng
Gentoo/Linux on DELL D600 1.4Ghz 
98% Microsoft(tm) Free!! 
Neuromancer 08:59:26 up 12:07, 6 users, 
load average: 0.58, 0.52, 1.04 

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