[nycbug-talk] Stablity fixed??? Maybe???

[Louis Bertrand]

On Fri, 1 Jul 2005, Matt Juszczak wrote:

> Hi all,
>
> Part of this message I cross posted to freebsd-questions, but no one there is 
> going to give me a good answer ... so I'd like a 2nd opinion :)
>
> After removing IPF and having a week of stability, we decided to put
> our mail server to the test today.
>
> I began flooding it with tons of mail messages using smtp-source at about 2 
> pm today.  The server load jumped up to about 4.50 average.  It eventually 
> started denying requests, but after waiting a few minutes, it would accept 
> them again (I was literally flooding it, I sent in all 1.2 million emails).
>
> I wrote a scipt to hammer it, so even after it would refuse the connection,
> it would hammer it again.  Eventually, the machine started to not respond.
> I could ping it with successful replies, but could not SSH into it.  The
> last message on the screen was "Could not write to /var/mail/thissucks",
> which was the account we were testing.
>
> I rebooted the machine, and all is fine.  I'm not sure if this is still a
> sign of instability, or if this is a "Any idiot who would sent 1.2 million
> emails and a full flood for hours to a mail server should expect something
> like this to happen" message.
>
> Any input?
>

Maybe you filled up the partition that holds /var/mail?
It could also be a file lock on the actual mailbox file.
Or maybe you're running out of memory and the disk drive
is getting hammered by both mail and swapping.
Basically, get a hunch of where the problem is and devise
some instrumentation to confirm it or rule it out.
At the very least, monitor with top(1), systat(1) and friends.

Ciao
  --Louis  <louis at bertrandtech dot ca>