I have some more info on this subject:

The big performance gap I noticed on different systems
is probably because of different harddisks.
IDE harddisks on W2K systems obviously use a write-cache
as default. So these systems were fast.
When using SCSI, the performance is really bad, compared to
IDE.

But this does not explain why a commit still has to last THAT long.
Sometimes more than one or two seconds.
Somebody told me that a commit is not much more than just setting
a kind of flag. So I wouldn't expect a lot of pages to be written!?!

Maybe someone can guide me to the parts of the sourcecode, where
I can find out what exactly is done, when the server gets a commit
message.

-- Heiko