The 20-terabyte size of the Library of Congress is widely quoted and as far as I know is derived by assuming that LC has 20 million books and each requires 1 MB. Of course, LC has much other stuff besides printed text, and this other stuff would take much more space.
Thirteen million photographs, even if compressed to a 1 MB JPG each, would be 13 terabytes.
The 4 million maps in the Geography Division might scan to 200 TB.
LC has over five hundred thousand movies; at 1 GB each they would be 500 terabytes (most are not full-length color features).
Bulkiest might be the 3.5 million sound recordings, which at one audio CD each, would be almost 2,000 TB.
This makes the total size of the Library perhaps about 3 petabytes (3,000 terabytes).
Not quite pocket-sized yet, but frighteningly close. If the LoC is 3 petabytes, we're at the point where I could mindlessly surf to Buy.com and get 3,000 1TB external drives for $200 each:
...and store my own personal LoC for $600k. That's cheaper than a lot of houses here in Boston. And that's just the stupidly inefficient way to store a personal LoC.
(With peer-to-peer, of course, the problem of giving me instant access to the LoC from my portable phone is essentially solved. The movies are still a bit slow.)
