How hard drive store data and its parts

A computer hard drive (HDD or hard drive) is needed to store information after turning off the computer, in contrast to RAM ( random access memory ) – which stores information until the power is cut off (before turning off the computer).

The hard drive, by right, can be called a real work of art, only engineering. Yes Yes exactly. It’s so complicated everything is arranged inside. Currently, around the world, a hard drive is the most popular device for storing information. It is on a par with such devices as flash memory (flash drives), SSD. Many people have heard about the complexity of the hard drive device. They are perplexed as to how much information is placed in it. And therefore would like to know how the hard drive of the computer is built or what it consists of. Today there will be such an opportunity).

Computer hard drive device

The hard disk consists of five main parts. And the first of them is an integrated circuit that synchronizes the operation of a disk with a computer and controls all processes.

The second part – an electric motor (spindle), makes the disk rotate at a speed of about 7200 rpm, and the integrated circuit keeps the rotation speed constant.

And now the third, probably the most important part, is the rocker arm, which can both write and read information. The end of the beam is usually divided so that you can work with multiple disks at once. However, the rocker arm never comes into contact with the discs. There is a gap between the surface of the disc and the head, the size of this gap is approximately five thousand times smaller than the thickness of a human hair!

What if the gap between disc and head disappears?

(You may skip this part if you don’t want to get into the details) Let’s see what happens if the gap disappears and the rocker arm touches the surface of the rotating disk. We still remember from school that F = m * a (Newton’s second law, in my opinion), from which it follows that an object with a small mass and tremendous acceleration becomes incredibly heavy. Given the huge speed of rotation of the disk itself, the weight of the rocker head becomes very, very tangible. Naturally, disk damage is inevitable in this case. By the way, here’s what happened to the disk, for which for some reason this gap disappeared:

The role of the friction force, i.e. its almost complete absence, when the beam begins to read information while shifting up to 60 times per second. But wait, where is the engine here, which sets the beam in motion, and even at that speed? In fact, it is not visible, because it is an electromagnetic system that works on the interaction of 2 forces of nature: electricity and magnetism. This interaction allows you to accelerate the rocker to the speeds of light, in the literal sense.


The fourth part is the hard drive itself, this is where the information is written to and where it is read from, by the way, there can be several.

Well, the fifth, final part of the hard drive design is, of course, the case. In which all other components are installed. The materials used are as follows. Almost the entire body is made of plastic, but the top cover is always metal. The assembled case is often called the “hermetic zone“. There is an opinion that there is no air inside the containment zone, or rather, that there is a vacuum. This opinion is based on the fact that at such high speeds of rotation of the disk, even a speck of dust that gets inside can do a lot of bad things. And this is almost true, except that there is no vacuum there – but there is purified, dried air or neutral gas – nitrogen, for example. Although, perhaps in earlier versions of hard drives, instead of purifying the air, they simply pumped it out.

How and in what form data is stored on the computer’s hard drive

Data is stored in narrow tracks on the surface of the disc. During production, more than 200 thousand such tracks are applied to the disc. Each of the tracks is divided into sectors.

Maps of tracks and sectors allow you to determine where to write or where to read information. Again, all the information about sectors and tracks is in the memory of the integrated circuit, which, unlike other components of the hard drive, is not located inside the case, but outside and usually below.

The surface of the disc itself is smooth and shiny, but this is only at first glance. On closer inspection, the surface structure is more complicated. The fact is that the disk is made of a metal alloy coated with a ferromagnetic layer. This layer does all the work.

The ferromagnetic layer remembers all the information, how?

Very simple. The rocker head magnetizes the microscopic region on the film (ferromagnetic layer), setting the magnetic moment of such a cell to one of the states: o or 1. Each such zero and one is called bits. Thus, any information recorded on the hard disk, in fact, is a certain sequence and a certain number of zeros and ones. For example, a good-quality photograph occupies about 29 million such cells and is scattered across 12 different sectors. Yes, sounds impressive, but in reality – such a huge number of bits occupy a very small area on the surface of the disk. Each square centimeter of the surface of a hard drive includes several tens of billions of bits.

The principle of operation of the hard drive

We have just examined the hard drive device, each of its components individually. Now I propose to link everything into a certain system, due to which the very principle of the hard disk will be understood.

So, the principle by which the hard disk works is as follows. When the hard disk is turned on, it either writes to it, or it reads information from it, or the OS is loaded from it. The electric motor (spindle) starts to gain speed. And since hard the disks are fixed on the spindle itself, respectively, they also begin to rotate with it. And until the revolutions of the disk (s) have reached the level so that an air cushion forms between the rocker arm and the disk. The rocker is in a special “parking zone” to avoid damage.

As soon as the revolutions reach the desired level. The servo drive (electromagnetic motor) drives the beam, which is already positioned in the place where you want to write or where to read the information. This just contributes to the integrated circuit, which controls all the movements of the rocker.

There is a widespread opinion, a sort of myth, that at times when the disk is “idle”. That is no read/write operations are temporarily performed with it, the hard drives inside stop rotating. This is really a myth, because, in fact, the hard drives inside the case rotate constantly. Even when the hard drive is in energy-saving mode and nothing is written to it.

please share this posts if you liked our detailed post. It takes a lot of time to write such articles. Please read more, share more and please comment below if you found our article interested.

Leave a Comment