Factory Marking of Hard Disk Drive Magnetic Surface (Low-level Formatting)
Marking on sectors in hard disk drives is made during the manufacture of the disk drive by record servo marks which are created by means of the special high-precision external mechanical device through a technological window in the hermetic block on magnetic disks; after marking completion the technological window is stuck up. The laser gauge of distance is used for the control over moving of magnetic heads during marking. Servo marks are put on a working surface of a magnetic disk, forming the cylindrical tracks located on identical distance from the centre of rotation of a magnetic disk. Each track is formatted on different sectors quantity depending on the length of a circle, providing a constant record density.
At usual operation of a hard disk drive servo marks, being located between sectors, are selected from the data stream of the disk drive and are used for keeping a magnetic head over the required track irrespective of external effects and thermal deformation of elements, and also for identification of sectors and stabilization of frequency of rotation of a magnetic disk by spindle motor. Servo information is a basis of marking of a disk and in case of its damage the hard disk drive controller cannot restore it by itself. Usually it is accompanied by positioner knocking at mechanical limiters and disk drive "hanging up".
In ATA-3 standard the application of factory marking of a magnetic disk on sectors in hard disk drives resulted in refusing the command "Format track" with a code 50h. For the same reason the procedure of low level formatting (Low-Level format) was eliminated from BIOS of modern motherboards. In spite of it, a myth about the possibility of program low level formatting which generates the creation of "noddy" programs, simply filling hard disk drives with zeros and erasing the information from it, still persists in network.