Factory Layout (Formatting) of the Hard Drive
The creation of a magnetic surface without defects is almost impossible; therefore, the technical operation of the search of the sectors incapable of storing the information reliably is made after mapping of servo marks at hard disk drive assembly at a factory. During the search of defects, the sensitivity of magnetic heads is artificially reduced that allows detecting unstable sectors which can develop into defects. The list of addresses of bad sectors is used for the creation of the data structure named the translator. The translator data links a logical number of the sector to its physical position on a magnetic disk and is located in the area unavailable to the user; this area is used by hard drive electronics only. The found bad sectors are not used at translator creation; therefore, the logical sequence of stable sectors is linear. The translator of hard disk drives hides the physical format of disk drives - that is why the number of cylinders, sectors and magnetic heads printed on the case of an HDD does not correspond to their real values. This way of concealment of defects was given the name "the method of the skip of the sector" or "low-level formatting" of the hard drive. After factory testing and the creation of the translator, the storage device goes on sale without any bad sectors.