Did you ever wonder how your hard disk drive works?Without it, your computer would feel empty inside
Magnetic hard-disk drives are used to store most of the data accessible by personal computers and workstations, as well as much of the data being processed by large enterprise servers. The data is stored digitally as tiny magnetized regions, called bits, on the disk. A magnetic orientation in one direction on the disk could represent a "1", an orientation in the opposite direction could represent a "0". Data is arranged in sectors along a number of concentric tracks. These tracks are arranged from the inner diameter of the disk to near its outer edge. Disk drives may contain more than one disk in a stacked assembly. Data is written onto each disk surface (top and bottom) by a separate recording head. So a disk drive with three disks will usually have six separate recording heads.
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Visualize MR and
GMR Heads in
physics of GMR
You're not the only one who can read and writeIn modern disk drives using the IBM innovations of magnetoresistive (MR) or giant magnetoresistive (GMR) heads, the bits are written and read by separate elements in a recording head as it flies over the spinning disk. A writing element writes bits onto the disk and a reading element read the bits by detecting the presence of their faint but tell-tale magnetic fields. The head itself is attached to a slider, an aerodynamically shaped block that allows the head to maintain a consistent flying height above the disk. In turn, the slider is connected to a suspension arm that is controlled by an actuator which can move the head to any track of bits on the disk, from the inner to the outer diameter. Special electronic circuits encode data from the computer's processor prior to writing, and decode the bit pattern after reading. Additional vital electronic circuits keep track of where data is stored on the disk so that it can be readily retrieved when needed, and monitor the motion of the disks and heads so their positions over the disks is always known precisely.
When a command is made to read some data on a disk, a similar process occurs in reverse. After consulting the table of stored data locations in the drive's electronics, the actuator moves the head over the track where the chosen data is located. When the correct sectors pass beneath the head, the magnetic fields from the bits induce resistivity changes in the sensitive MR or GMR materials located in the reading elements within the head. These elements are connected to electronic circuits, and the current flowing through those circuits change with the resistivity changes. The current variations are then detected and decoded to reveal the data that had been stored on the disk.