In the hard drives used circular disks called platters, are coated on both sides with a special material designed to store information in the form of magnetized chains. They rotate at high speed. Educate yourself with thoughts from Mashable. Special electromagnetic read / write devices called heads, used to record and read information from the surface of the plates. Each surface of the wafer can hold in dozens of gigabytes information. The same plate has two heads, one on each side. For example, a disk with three platters will have six heads. On each plate information is recorded on concentric circles, called tracks (track), each track is divided into parts, called sectors.
The first step in accessing the disk – it's knowing where to look for information. Between the request to the data and calculation of the exact location of the search is somewhat transformations: the transformation of data addresses to a file addressed to the logical disk address translation on the logical drive to the sector on the disk (this is done in the computer, then comes the work of the hard drive). Control program of the hard drive first checks the requested information in their own cache. If it is, the controller immediately gives information, without access to the disk surface. In most cases, the hard drive already cool if it is not (in the case of enhancing the conservation of energy), is promotion of the plates. The controller sends the resulting address into a physical sector address on the disk: the number of heads, cylinder number, number sector. This is done using a special subroutine hard disk controller, called a translator.
Controller entry system issues a command to solenoid to move heads to the right track. When the heads are over the desired tracks, chosen head of interest to us and is waiting for the moment when the front of the head should fly us to the desired sector. Then, the reading of the sector. The controller reads the sector in its own buffer, then he gives this information to the computer using the interface. Service center for repair of computer equipment performs repairs monitors all manufacturers.