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You can get up to 10TB drives for around $720 right now:

http://www.amazon.com/Seagate-Enterprise-Capacity-200RPM-ST10000NM0016/dp/B01DAI6JUS?ie=UTF8&keywords=10tb hard drive&qid=1462821202&ref_=sr_1_5&sr=8-5

Or 8TB drives go for just over $200:

http://www.amazon.com/Seagate-Archi...qid=1462821259&sr=8-1&keywords=8TB+hard+drive

I'm using the 8TB of the above in my 5,1 with no problems.

I tried using the HGST 10TB drive (https://www.pcnation.com/web/detail...00-10-Tb-3-5-Inch-Internal-Hard-Drive-0F27452), and for some reason it won't spin up inside the 5,1 but will work on an external USB drive bay. Not sure if it's a matter of juice or what.
the HGST 10TB drives only work if you cover the leftmost 3 pins of the power connector with some non-conductive tape, or block them off with some other method.
 
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