Majed B. wrote:

Your applications can request as much files as they want regardless of
their location, but the mechanical heads move together, so they can be
at a single location at a point of time reading a single stream of a
file (or multiple files if they were next to each other on the
physical platter).

Yes that's completely correct, and it's the job of the "elevator" (*) on the 
"md" code to decide which sector, and in what order, such sectors will be 
serviced. If the "elevator" is aware of the underlying hardware, it will do 
the right thing if there are several md or just one.

*(I am not an expert on this, is just what I got from Robin)

-- 
Antonio Perez