Hi, I wrote this post. I see that everyone is as confused as I was with the "milliards de milliards" :) "Millions of trillions" is the right way to say it in English I believe (if you don't want to go over trillions). I edited the headline a couple of minutes after publishing to correct my mistake. Sorry!
basically 3 million 1TB hard drives in raid 5 (1M x 3). you can probably fit a 500 1TB 2.5" drives into a single rack if you really try, and 2,000 racks can fit easily into warehouse-sized facility. (grid of 100 x 20 racks)