Re: Multiple arms
This has been done, and didn't prove cost effective. The RW arms are not cheap, adding more increases vibration so you can't get as much density unless you move the arms in unison so one arm isn't moving while the other is trying to read/write...
If they haven't been this work in all the years when they had tons of money to invest in new hard drive technology, they sure won't now when SSDs have taken the high end off the market and drive makers are barely able to break even.