Very. We have a single Linux box facing the Internet which
runs everything through postfix, amavisd, and clamav to weed out
the phishing and worms that attack the Microsoft virus, Windows,
then hands off messages that pass to the internal cluster using
round-robin DNS as the poor-mans load balancer. This box runs
with a load average less than 1.00 most of the time, rejects
close to 2 million messages a day on IP related tests, passing
about a half-million through to the internal servers which do the
spamassassin checking and delivery to the user's mail stores.
What processing and i/o power do you have on that box and how much RAM?
For the front end boxes, I had about 20-30 dual PIII 800Mhz boxes with
two SCSI disks and 1GB worth of RAM. They reject close to 180 million
messages based on access and ip rules, header and body checks (so
nothing cpu heavy) and they pass on about 3 million for routing or
further processing.
The border MX machine is running a Intel(R) Pentium(R) 4 CPU 3.20GHz, seen
as two processors in /proc/cpuinfo with 6389.76 bogomips. It has 2GB RAM,
and currently has a load average of 0.24 reported by top.
I guess that is plenty for one third the volume of rejects one of those
dual PIII boxes handled...but then your box handles five times as many
deliveries and therefore scans...
The hard drive is a 40GB WDC WD400JD-19LS SATA which isn't anything special
by any means. It's running SLES9, installed in February 2006. Uptime is
only 356 days as it had to be rebooted to move things around in the rack.
You make sure emails never queue eh?
The machines handling mail deliver in the cluster vary. The first one I
checked has an Intel(R) Celeron(R) CPU 2.66GHz with 1GB of RAM. These too
have pretty vanilla SATA drives.
The main server with the home directories has an Intel(R) Pentium(R) 4 CPU
3.00GHz with no SMP, 2GB RAM, and several SATA drives.
The border MX isn't beginning to breath hard handling the IP access rules,
postfix, amavisd, and clamav. We have seen very even distribution amongst
the delivery machines in the cluster using nothing more for load balancing
than dnscache from djbdns for a single hostname on the private internal
10/100 LAN.
Heh, I cannot imagine any other software for dns caching.
The attached image shows the size of the mail queues on each of the 4
machines every fifteen minutes since midnight yesterday. This peaks
shortly after midnight when daily security scans and other maintenance jobs
are running.
The load averages on these cluster machines rarely gets over 1.00.
The only times I had high load averages was when sendmail was in and
when we are under bounce floods/ddos.
I guess this is the cheapest and most efficient way to do email.
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