The HDD industry has a relatively short but fascinating history. In four decades it evolved from a monstrosity with fifty 24-inch diameter disks storing only 5 MB of data to today’s drives storing close to 100 GB (100,000,000,000) of data on one surface of a disk in a 31 2 inch drive. This enormous growth was made possible by developments in diverse fields of knowledge including materials, tribology, mechanics, servo control, signal processing and electronics. Drives of first generation were significantly different from the drives we see now in aspects like size, capacity, and data transfer rate as well as in the technologies used. For a comprehensive reading on the history of magnetic recording in general and hard disk drive in specific, interested readers may refer to many published articles such as [5], [74], [186].
The Early Days The fascinating journey of this marvelous device began with a huge, monstrous equipment called RAMAC (Random Access Method of Accounting and Control), which used the very first non-volatile DASD introduced by IBM in 1956 [151]. The disk drive of RAMAC contained fifty disks, each 24 inch in diameter, and could store 5 Megabytes of data at a recording density of 2K bits/in2. The track density and linear density were 20 TPI and 100 BPI, respectively. The disks used to be spun at a speed of 1200 RPM (revolutions per minute) and the rate of data transfer was 8.8 kilobytes per second (KB/s) only [74]. The RAMAC did not use any closed loop control for the head positioning mechanism. IBM, the only company designing and building hard disk drives in the early years, was the sole contributor to the growth of this industry in those days. It designed in 1961 the first drive using air bearing heads, and in 1963 the first removable disk pack drive. All these drives used either motor-clutch mechanism or hydraulic actuators for the head positioning system operated under open loop control. The first HDD with a closed loop servo control was produced in 1971 (IBM 330 Merlin Drive), and it used the position of the head relative to the track sensed from the disk. In 1973, IBM introduced another model of HDD (IBM 3340) that used head and slider fabricated on ferrite. It contained 2 or 4 disks of 14-inch diameter. The storage capacity was 35 MB for a drive with 2 disks; data transfer rate was 0.8 MB/s. The areal density on the recording medium reached 1.69M bits/in2. These drives were known as Winchester drives. This was the first HDD to use the servo control loop found in disk drives nowadays [157].