On Wed, Jan 05, 2000 at 03:01:51PM +0100, Thomas Michael Wanka wrote:
> He described a mail server with extreamly heavy load, something 
> nobody would run without a UPS. My APC shuts down the linux 

This can happen even on a ligthly loaded mail server: your server is down,
mails get accumulate on relays. server comes back up, relays start flusing
their queue. In this situation the load can be higth.
For UPS: my UPSes shut down the machine when they are low on battery; but I've
got brutal power shutdown anyway (maybe it's a bug in the UPS - anyway this
can happen).

> server without problems. The other "misterious" thing is there is no 
> investigation done what caused the problem, it could be the OS or 
> the MTA, the mail server software, incompatibilities between these or 

I think anybody with a little filesystem knowledge can do the analysis:
fsync() doesn't behave properly on linux. This is not a bug but a design
desision (at last it's what the ext2 developers says): no write ordering,
which means you don't have up-to-date metadata when the data gets flushed.

For sure a linux system will work in this situation, and for such system
an UPS is recommended. But this doesn't prevent exeptionnal events from
happening and in this case I maintain NetBSD is better than linux (this is
what I said in my original mail).

--
Manuel Bouyer, LIP6, Universite Paris VI.           Manuel.Bouyer@lip6.fr
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