hard disc - benchmark problem freebsd5.3

[oliver walland]

I will try to explain the problem in a short way:

2 situations (same Hardware):
bonnie -d /usr -s 1024, during bonnie just iostat for looking the throughput

First Situation:
On the first Channel of PATA jumpered as master the hard disc und second
channel as master a cd-rom
Throughput about 15mb/s (iostat)

Second Situation:
Just plugged the cd-rom off.
Throughput about 35mb/s (iostat)

This is very strange; I tried this on several PC's. It is always the same.

I do not believe that I am the only person who has this problem. I also got
a strange problem with testing SATA RAID5 controller (PCI64). Throughput is
about 130mb/s, if I make bonnie at the same time on the onboard lsi
controller, it goes down to 50mb/s. These are different controllers and
channels, so what is wrong. I think something really bad is going on.