Disk Evolution & Comparisons

Disk Storage
1950's disk held 5 million bytes
using a stack of fifty 24" platters
in a refrigerator sized cabinet

Similar disk cabinet today
holds over 5 trillion bytes
(or a million times as much)

Disk Drives
Typical desktop PC disk today has
100 to 200 gigabytes on a drive
the size of a paperback novel
Typical portable or handheld device
(PDA & Tablet PC) has 20 to 40 gigabytes
on a disk the size of a U.S. dollar coin.

one byte = an 8 bit character,
kilo (K-byte) = thousand
mega (M-byte) = million 		giga (G-byte) = billion
terra (T-byte) = trillion
peta (P-byte) = terra x 1,000

Removable/Portable Storage
Flash memory sticks (USB storage devices) the size of a car key for transfering data between desktops or laptops hold 2 gigabytes of data

Flash memory cards the size of a quarter (up to a gigabyte) for handheld devices like phones & cameras

Perspective... In 50 years the disk has shrunk from a 24 inch platter to less than 2 inches and holds over 10,000 times the data...all this while dropping in cost by a factor of 100,000 per megabyte... much the result of similar increases gained in disk densities & manufacturing volumes.

Today's computer centers often have disk arrays holding several peta-bytes of data...in 7x24 fail safe operation.

---by comparison, the entire contents of the United States Library of Congress requires about 20 terabytes.

It's somewhat humbling to think that a person's lifework, say, the collected works of Shakespeare and several others will easily fit on a single device the size of a quarter.

Put a another way, in 100 terabytes one could store the entire accumulated knowledge of the human race with room to spare.
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