The advise about using tcpserver is very sound, not just because of the
binding benefits.
The other benefits are that you can constrain resource consumption nicely.
Eg, on a 256M system that is, say, just doing inbound smtp, you might use
tcpserver to constrain the concurrency to 250 or so. You might also set
resource limits for tcpserver (which are then inherited by qmail-smtpd) so
that no single smtp session can consume more than, say 1M of memory.
This way, the worst thing that can happen is that an smtp session will be
deferred. The benefit is that you know that the system cannot be overloaded
by external connections - malicious or otherwise.
I tend to log and graph the tcpserver output that way I can see peak session
usage trends over time, which tell you how close you are to running out of
resources.
Mark.
At 04:31 PM Friday 8/6/99, Cris Daniluk wrote:
>Well, we're starting into our testing of qmail so that we can transition
>away from the garbage-polluted ms smtp server that we had such a long thread
>about earlier this week.
>
>Basically, we constructed a temporary system for benchmarking. It is a dual
>p2 400 with a dpt smartraid5 controller and 64mb cache. We put in 2 9.1gb
>cheetahs on a raid 0 stripe. The system has 160mb ram.
>
>The first benchmark we ran was to see how fast we could populate the queue.
>I made a script to sequentially fill the queue with 20kb messages. It was
>able to do 2000 20kb messages in approximately 16 seconds (precision was
>only to the second, so 15.1-16.9 are valid ranges). 125 messages per second
>is more than adequate for our needs. I was very impressed by the fact that
>qmail could populate the queue so quickly. I think that definitely goes to
>show the scalability of qmail.
>
>The next test we're going to do is to use it as a mail relay, relaying from
>the message generator machines out to the net. For the short term, we are
>going to run 4 separate qmails with 4 separate queues. Each instance will be
>on a separate ip, though. What needs to be done to qmail to make it bind to
>a specific IP? This is pretty vital that we bind to separate ips because
>eventually we will be putting in 4 network cards (one for each queue).
>
>To further increase our hardware aresenal, once we find the optimal
>performance setup, we're going to build 5 of them. We'll have 5 machines
>generating mail, 5 sending, and we hope to be able to send upward of 10
>million or more per day. At that time we'll also have a 256mb cache on the
>raid controller so that the queue can run much more efficiently.
>
>I think that everyone on the qmail list deserves a big thanks from all of us
>for the valuable information and insight. It appears that qmail will be a
>successful solution for us, and ironically, thousands of dollars cheaper
>than the Big Hardware Big Software microsoft solution that we were using
>before.
>
>Once we get the network cards in and binded, we'll be on our way to a
>wonderful solution...
>
>Cris Daniluk
>MicroStrategy
