From: Wietse Venema (wietseporcupine.org)
Date: Mon Oct 02 2006 - 10:04:33 CDT

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Francisco Reyes:
> Adrian Ulrich writes:
>
> > Are you using Linux or *BSD?
>
> FreeBSD 6.1
>
> > Running something like iostat (Solaris /BSD?) or sysstat (Linux: http://perso.orange.fr/sebastien.godard/)
> > could give you a clue about how busy your Raid-system is:
>
> Have used iostat and I see lots of small transactions.

On FreeBSD, this gives cpu, memory, disk utilization and more:

    systat -vmstat

> > Otherwise your SQL-Server may be the bottleneck.
>
> Eliminated 2 of the 3 SQL lookups and plan to remove the 3rd today.
>
> > You could try to decrase the number of smtpd processes (master.cf) or
> > play with *_destination_concurrency_limit on your frontend servers.
>
> Ideally I would like to decrease incoming mails only to these two machines.
> Other machines are fine.

If none of cpu/memory/disk are saturated, then it's likely waiting
for things going across the network.

"netstat -I" can identify problems with collision or bad packets;
"netstat -s" can help to identity trouble higher up the network
stack.

        Wietse
>
> > How about spreading the heavy-domains across multiple backends?
>
> We have 4 mailstores. These two have the better hardware so we moved the
> heaviest smtp traffic domains to these two machines. I am still trying to
> convince the powers that be.. to get a SCSI setup for these domains.
>
> > You are using Maildir, correct?
>
> Correct. Maildir run off Courier IMAP, serving imap and pop3.
>
>

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