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April 18, 2002

Terabyte Territory: article on disk technology

Amercian Scientist: "Terabyte Territory" by Brian Hayes is a splendid article on the history of the magnetic disk drive. 

Hayes notes that if we extrapolate the growth rate of disk drives over the last five years, today's 120 gigabyte drive will be a 120 terabyte drive in 2012.  Hayes asks what you would do with that much space:

One certainty is that you will not fill the void with personal jottings or reading matter. In round numbers, a book is a megabyte. If you read one book a day, every day of your life, for 80 years, your personal library will amount to less than 30 gigabytes, which still leaves you with more than 119 terabytes of empty space. To fill any appreciable fraction of the drive with text, you’ll need to acquire a major research library. The Library of Congress would be a good candidate. It is said to hold 24 million volumes, which would take up a fifth of your disk (or even more if you choose a fancier format than plain text).

Other kinds of information are bulkier than text. A picture, for example, is worth much more than a thousand words; for high-resolution images a round-number allocation might be 10 megabytes each. How many such pictures can a person look at in a lifetime? I can only guess, but 100 images a day certainly ought to be enough for a family album. After 80 years, that collection of snapshots would add up to 30 terabytes.

What about music? MP3 audio files run a megabyte a minute, more or less. At that rate, a lifetime of listening—24 hours a day, 7 days a week for 80 years—would consume 42 terabytes of disk space.

The one kind of content that might possibly overflow a 120-terabyte disk is video. In the format used on DVDs, the data rate is about 2 gigabytes per hour. Thus the 120-terabyte disk will hold some 60,000 hours worth of movies; if you want to watch them all day and all night without a break for popcorn, they will last somewhat less than seven years. (For a full lifetime of video, you’ll have to wait for the petabyte drive.)