ABSTRACT
Hard disk drives (HDDs) were invented by R. Johnson in 1954 and were introduced by IBM 2 years later as an alternative to the then existing magnetic storage devices such as magnetic drums and ¨oppy disks (Harker et al., 1981; Stevens, 1981). ˜e Ÿrst HDD, weighing over one ton and shown in Figure 64.1 (Wikipedia, 2010), does not bear much similarity with its modern counterparts. It used 50 disks to store information data, which were read and written by two transducers. Each transducer was embedded in an externally pressurized head, as shown in Figure 64.2 (Harker et al., 1981). During the HDDs’ operation, compressed air was supplied to the head such that the head was positioned hundreds of micrometers from the disk. Since this HDD had only one pair of heads, the heads needed to move from one disk to another in order to read/write information data on diµerent disks. ˜e Ÿrst generation HDDs needed regular maintenance, and IBM leased them to their customers for $3500 per month, instead of selling them (Wikipedia, 2010).
