Could they be using tape drives? This wikipedia entry says limits of 35TB were achieved in 2011 and limits of 185TB were achieved in 2014. The 2011 achievement wasn't expected to be commercially available for 10 years. Would that also preclude industrial/government availability?

http://en.wikipedia.org/wiki/Tape_drive#Capacity

Edit: Ha, nevermind, even if they had 185TB tape drives, they'd still need 5 billion of them (unless my math is way off).