If you're ever had concerns about the effect of noise on your disk performance, let Brendan Gregg put your mind at rest. Thanks to the brilliant Analytics (aka Dtrace with a brilliant web interface) on the a Sun Storage 7410 we can clearly see noise does have an effect, and in this extreme case (don't try this at
home work), quite a large effect:
Now that is cool. Lets see NetApp or EMC show us that kind of real time proof.
Brendan has a full report and some screenshots of the Analytics output here.