History of Hard Disks

The very first hard drive was invented by Reynold Johnson, of IBM. The IBM 350, which was released in 1956, and was called a “Random Access Method of Accounting and Control”. It was a cylinder that was capable of storing 4.4 megabytes. It was leased for $3,200 a month. These IBM hard disks ranged in capacity from 4.4 megabytes in the beginning, up to 22 megabytes.

 The cost per megabyte, and the average size of the hard drive have change dramatically over the years.

http://en.wikipedia.org/wiki/Hard_disk

http://en.wikipedia.org/wiki/History_of_hard_disk_drives

http://en.wikipedia.org/wiki/Early_IBM_disk_storage

http://www.disktrend.com/5decades2.htm

http://upload.wikimedia.org/wikipedia/commons/a/a1/Hard_drive_capacity_over_time.png

http://www.alts.net/ns1625/winchest.html

How they are put together

Hard drives have an interesting set of components. Each hard drive has a motor, a spindle, a set of platters, a read/write head, an actuator, a circuit board, and an air filter. Data is recorded in a spiral. Hard drives have multiple platters, and each one has its’ own read/write head. Modern platters are made out of either glass, or ceramics, and have a magnetic material deposited on it. The platters are monted on the spindle, which spins at speeds between 5,400 and 150,000 revolutions per second.

The read/write head on modern hard drives, at rest, lay upon the drive platter. However, when the platter starts spinning up, an air foil creates a pocket of air upon which the read/write head floats. (This technique was introduced by IBM in its’ Winchester hard drive in 1973) When the power is cut, the head will crash into the surface of the platter, called a “Hard drive crash.” This is a bad thing, as it ruins the surface of the disk. To prevent this, springs are attatched to the head to pull the head back in — it will continue floating on the spinning surface of the disk  until it winds down, and by that poing, the head will be in the ‘landing zone’, a place where the head can rest when the disk is not spinning. The entire head assembly is on a lever. The position of the read/write head is actuated by a voice coil, which is used in telephones.

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http://www.duxcw.com/digest/guides/hd/hd4.htm

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http://www.duxcw.com/digest/guides/hd/hd5.htm