Search for 'adding second disc drive' in these forums. Once disk is added, simply create your ibays and you are done
Life is not so difficult after all. sme is designed for all of this. don't try to reinvent the wheel

If I had the need to share all my mp3's on a seperate drive, I would mount this drive as
mount /dev/hdd /home/files/ibays/mp3
and that whole drive will now hold the mp3 ibay.
if I were to add another drive that holds the files in the mp3 ibay than I would
mount /dev/hdc /home/files/ibays/mp3/files
needless to say, when you add a drive to a mount point, than whatever was there originally would not be visible anymore. So if you have content to preserve, move it somewehere else for the time being and copy it to you new drive afterwards.
kees