Business Week states that, "In ten years, the volume of online data accessible either on the Internet or on corporate networks is expected to approach a yottabyte..."

Currently, the largest named measure of data is the yottabyte (YB), which is exponentially greater than the zettabyte, exabyte, petabyte, terabyte, and so on. The yottabyte is approximately equal to 5X * 10^6, where X is equal to all printed matter that exists on our planet. More definitively, 1 YB=2^80 Bytes.

The highest-density digital tape (which is the highest-density medium currently in common use) made by one of the world's leading manufacturers stores data at a density of 124,000 bpi (bits-per-inch). Assume zero overhead for error-correction and -detection.

At a tape thickness of 8.9 microns, what must the diameter of a roll of tape be in order to store one YB of data, assuming that it is wrapped around a spool with a diameter of 0.5 inches and assuming that there is no space between the layers of tape?

Let's see numerically how big this spool is.

D = 2 * R = 2 * √(V3/Wπ)
D = 2 * √((L*W*T + .25*W*π)/(W*π))
D = 2 * √( L*T/π + .25 )
D = 2 * √( (2^80*0.03937*8.9) / (15500*1000*π) + 0.25 )

(using a calculator)....
D = 2 * √ (8.6991*10^15)
D = 2944 miles
For comparison, the diameter of the earth at the equator is about 7900 miles, and the diameter of the moon is about 2100 miles. That's a rather large roll of tape!

Posted by Ender on 2002-10-14 06:54:24