Somehow I expected a very quick reply from you. :-)
My comments on kernel mode were based on profiling data that I collected.
The profiling data showed the time to be in process/thread creation, not
I/O.
I know that exim is nasty on the disks. I've run tests with EXT3 and
Reiser, with mixed results. Both of those are journalling file systems so
I expect there to be more writes than usual. What is recommended ? Does
it make sense to run EXT2? (I plan to measure and find out.)
On my system exim is generating about 1000 disk writes per second. The
1000 disk writes are spread across 6 disk drives. I'm on an iSeries
running Linux, so the disk performance is hard to quantify - there is a lot
of double buffering going on. Regardless, my measurements didn't point me
at disk - it was CPU bound on my box, and most of the time was in the
kernel. (Of which I think it was process creation, based on the profile.)
Disk may be a problem, but I don't think it is one on this box yet.
Network thoughput didn't seem to be a problem either - at most it pushed
300KB a second. My 100Mb/s network cards and switch shouldn't even be
blinking at that rate. (Message sizes in this test don't seem to be very
large.)
