The presumed yottabyte capacity of the new Utah Center of the NSA, about which I commented a few days ago, is still making the rounds on news channels and news cites. Someone calculated that a yottabyte is equivalent to 500 quintillion printed pages. CNN helpfully added that a stack of paper with this many pages could reach all the way to the Moon and back 66 million times.

What they ought to have calculated is the size and volume of 250 billion 4 TB hard drives.

A lighter hard drive weighs about 0.4 kg. 250 billion of them? That would be 100 billion kilograms. Or 100 million metric tons. Or roughly 1000 of the largest cargo ships, each the size of a small city, filled to capacity with hard drives.

A hard drive is about 15/16″ tall. That’s 2.38 centimeters. 250 billion of them? Why, it’s a stack tall enough to reach all the way to the Moon and back 8 times.

The volume of a standard hard drive is about 342 cubic centimeters. 250 billion? That would be just a tad under 0.1 cubic kilometers (8.56 × 107 cubic meters, to be a bit more precise). That would be a field that is a kilometer square, filled with hard drives to the height of a small-ish skyscraper, about 25-30 stories high. Large as the Utah facility is, it’s by no means large enough.

Some might want to point out that if the NSA used flash memory instead, the volume (and also the power consumption) would go way down. True. But the price would go up. Flash memory is still roughly an order of magnitude more expensive than hard drives. So if the NSA wanted to build a yottabyte facility using flash memory, instead of spending 1.5 times the GDP of the entire United States, they’d be spending 15 times that amount. Or roughly three times the “gross world product”, estimated at 83 trillion US dollars.

Perhaps CNN and friends should do a little more math, not just to impress their readers but also to fact check the stuff that they report. Would be nice.

For illustration, I chose a Hungarian bank note from 1946, reportedly the highest denomination ever printed anywhere: it is a 100 quintillion pengő note. It is still far short of a yottapengő: you would need 10,000 of these banknotes. Then again, by the time hyperinflation ended and a new currency (the Hungarian forint, still in circulation) was introduced, the exchange rate was 400 octillion pengős to the forint; that would be 400,000 yottapengős.