HardDrives

7 Pages 1776 Words

Nearly every desktop computer and server in use today contains one or more hard-disk drives. Every mainframe and supercomputer is normally connected to hundreds of hard-disk drives. Hard disks were invented in the 1950s. They started as large disks up to 20 inches in diameter holding just a few megabytes. Hard drives were originally called "fixed disks" or "Winchesters" (a code name used for a popular IBM product). They later became known as "hard disks" to distinguish them from "floppy disk drives". Hard disks have a hard platter that holds the magnetic medium, as opposed to the flexible plastic film found in tapes and floppies. The earliest true hard disks had the heads of the hard disk in contact with the surface of the disk. This was done to allow the low-sensitivity electronics of the day to be able to better read the magnetic fields on the surface of the disk. The very first production hard disk was the IBM 305 RAMAC (Random Access Method of Accounting and Control), introduced on September 13, 1956. The RAMAC stored 5 million characters (approximately five megabytes, but a “character” in those days was only seven bits, not eight) on a whopping 50 disks, each 24 inches in diameter. Its arealdensity was about 2,000 bits per square inch; in comparison, today’s drives have arealdensity measured in billions of bits per square inch. The data transfer rate of this first drive was an impressive 88,000 bytes per second.
Over the succeeding years, the technology improved incrementally; arealdensity, capacity and performance all increased. In 1962, IBM introduced the model 1301 Advanced Disk File. The key advance of this disk drive was the creation of heads that floated or flew above the surface of the disk on an air bearing reducing the distance from the heads to the surface of the disks from 800 to 250 microinches. In 1973, IBM introduced the model 3340 disk drive which is commonly considered to e the father of the ...