Probably there is no such computer owner who would not want to know what a hard drive is. Some of idle curiosity, others - because of the need. It should be recognized that with the regular use of computer technology, among all the components, the hard drive appears to be the first contender for the “crash”. This is explained quite simply: in an average computer, this device is the only one in the design of which moving parts are used (fans and CD drives can be ignored).
Let's try to figure out what a hard drive is and why it is needed. You should be familiar with the device installed in almost every computer. According to the generally accepted definition, a hard drive (hard disk, hard drive, screw) is a storage device based on the principle of magnetization of a metal surface by an electromagnetic field. To understand what is at stake, it is enough to recall the audio and video cassettes, so popular in their time. In them, the recording head in a special way magnetized a tape with a magnetic layer (iron or chromium oxide ). Of course, such a comparison gives only a distant idea of what a hard drive is, especially since only the principle remains in the screws from the cassettes. To understand the issue in more detail, we will make a mental journey inside a classic computer hard drive.
A small rectangular metal box to which two wires are connected (an interface cable from the motherboard and power from the unit) is our goal. On the outside there may be holes sealed with labels with threatening inscriptions about how to unstick them. These holes are needed to equalize the pressure inside and outside the housing, which allows compensation for differences (necessary for operation). Inside are several glass or aluminum disks, on both surfaces of which a layer of chromium dioxide is sprayed.
Disks (plates, pancakes) are mounted on a common spindle, rotated by an electric motor with a constant speed (5400, 7200, 1000 rpm). This is the first construct. The second is a block of heads. A special frame, capable of moving between the plates in accordance with the commands of the controller, contains a number of magnetic heads. When power is supplied, the disks spin up, an air flow arises, due to which the heads “fly” above their surfaces at a distance of about 10 nm (there is no direct contact, as in cassettes). If the power is interrupted, then the frame is stepped by the positioning motor out of the area of the discs to prevent contact, and parked (fixed by a magnetic latch). The removal of the frame is possible due to the residual charge of the capacitors, which is enough to power the stepper motor.
Of course, this is a very simplified scheme, giving only a general idea of what a hard drive is. More information can be found on the web.
As already mentioned, the hard drive is one of the most used components. The operating system, applications and all user files are written to it. Recently, devices have appeared that are based on a completely different principle. These are solid state drives or SSDs. Since they do not have moving parts, the speed (often) exceeds the classic HDD. However, for the time being they cannot be recommended as a complete replacement for “screws” with magnetic disks, since the cost is much higher and the reliability is less (the number of read / write cycles is limited). By the way, there is nothing revolutionary in SSD drives - this is the same flash memory technology that every owner of a USB flash drive encounters.