I have a solution that would cost less than a $100 bucks to implement, and cheaper over the long run because it uses bare bones drives.
First off, I don't understand why anyone would need constant access to 40TB of files unless you were a business serving content on demand. For the average home user, why do they need to have 24/7 access to an enormous movie/tv show collection? Waste of money and electricity! Why not just keep everything stored on OEM drives on a shelf? Then put your collection on a database that tells you which drive the content is on. Do a search for the show you want to watch, then just pop the drive in and your good to go. Your drives won't wear down as fast because they will be sitting idle until you pop them in. And, you can add to the collection simply by buying a new drive.
The cost of 40 terabyte drives is relatively cheap if you buy them as needed. Then you buy a
Voyager Q dock and hook that to your computer via eSata or Firewire 800.
Anyone who needs constant access to 40TB of files needs to get out in the fresh air more often. However, 40TB sitting on a shelf waiting for the rare time you will watch it is way more efficient.