ahmad riza h nst put forth on 11/8/2010 3:05 AM:

> yes i read the manual before, it's said "Virtual aliasing solves one
> problem: it allows each domain to have its own info mail address. But
> there still is one drawback: each virtual address is aliased to a UNIX
> system account. As you add more virtual addresses you also add more
> UNIX system accounts. The next section eliminates this problem. "
> this what i want to understand about. how bad the system or the
> postfix it self if we use thousands of unix system account to host
> virtual users, or it just ok with it ?

You won't have local system accounts.  Just setup Postfix and Dovecot to
query your current mysql domain and user database.  It may take some
tweaking, but what doesn't? ;)

Are you using Dovecot for IMAP and POP or just POP?

> our hardware is hp dl180 g6 (a xeon quad core + raid 1 + 4G ram)

Ok, that answers one of my previous questions.  This system isn't nearly
strong enough for thousands of users.  You should:

1.  Bump the RAM up to at least 8GB
2.  Install the second matching quad core processor

Both of these things are relatively inexpensive, and it's better to
install them before the machine goes into production, so won't have
downtime when you find you need to install them later.

RAID1 implies only two disks with a single spindle of throughput.  One
spindle won't be nearly enough throughput for "thousands" of users.  At
minimum you should have an 8 disk hardware RAID5 array in your dl180 g6
for storing:

1.  System log files
2.  Postfix spool directoty
3.  Dovecot IMAP/POP mail store directories
4.  Mysql database if you choose to move it to this box
5.  Any other files with very high read or write access frequency

15k SAS drives would yield the best performance, but 7k SATA drives will
be considerably less expensive and offer greater capacity.  Regardless
of which you choose, you need vastly more than 1 spindle of throughput
for over 1000 users.  Given the relatively low cost of SATA drives, I'd
say you should install as many as will fit in the box, and configure
them as one RAID5 or 6 array, with one standby spare.

I highly recommend you use Dovecot LDA for mailbox delivery if offerig
IMAP, especially if you intend to configure ManageSieve.  Using LDA
updates the Dovecot indexes during delivery, decreasing MUA response
times, as the emails are already indexed when the user accesses an
email, instead of during the process of accessing the new email.  The
latter is the default indexing mechanism.

http://wiki2.dovecot.org/LDA
http://wiki2.dovecot.org/LDA/Postfix
http://wiki2.dovecot.org/Pigeonhole/Sieve
http://wiki2.dovecot.org/Pigeonhole/ManageSieve

-- 
Stan

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