Hard drive
A high-capacity, self-contained storage device containing a read-write mechanism plus one or more hard disks, inside a sealed unit.
A magnetic disk on which you can store computer data.
A single hard disk usually consists of several platters. Each platter requires two read/write heads, one for each side. All the read/write heads are attached to a single access arm so that they cannot move independently. Each platter has the same number of tracks, and a track location that cuts across all platters is called a cylinder.
A hard disk drive is composed of one or more platters, spinning disks containing tracks of magnetic information. These platters are read by read/write heads that hover just above the surface of the disk on a cushion of air created by the speed of the platter's rotation. These heads are attached to an armature that can move them over the surface of the disk, powered by a magnetic 'voice coil'. The platters generally rotate at either 5400 or 7200 RPM, and the movement of the read/write heads to separate areas of the disk is almost instantaneous.
Some important elements in hard drive operation include zones, tracks, sectors, servo system, and variable density. Inside the hard drive information is stored on platters and it’s written by heads while platters are spinning.
Modern drives use an embedded servo system which means the servo system information is located on all surfaces evenly. Servo System data can be written only at the factory and cannot be fixed or re-written during drive’s regular use.
External Link: HDD From Inside
