How does a computer hard drive (HDD) work? Hard drive: operating principle and main characteristics

HDD, hard drive, hard drive... All these words mean the same component of a modern personal computer, without which it is impossible to imagine it.

Previously, all information on computers, which at that time were called computers, was stored on devices called punched tapes. What is punched paper tape? Essentially, it is a piece of cardboard paper with special holes made in it. But this is the “stone age” of computers. The next stage in the development of personal computers was a technology called magnetic recording. It is this principle that underlies the operating technologies of modern hard drives. The main difference between hard drives of the past and modern models for ordinary users is the amount of information that can be recorded on one medium. If earlier this volume was measured only in kilobytes, today we are dealing with terabytes. Increasing the volume of stored information is one of the main achievements of current HDDs.

Why and what is HDD needed for?

Why do you need a hard disk (HDD) and how is it used directly by the computer operating system itself? As a rule, any computer stores some kind of information, and a hard drive is the very device on which the information is stored. Today this is a very important function for any computer (storing information on a digital medium), since without a hard drive we, users of personal computers, would have to have constant access to the Internet or local network, and computers without such capabilities would lose a significant share of their functionality.

In more “scientific” terms, a hard drive is a storage component of any PC. The main task of this component is to store information for a long time. A hard drive, unlike a computer's RAM (random access memory), is not a memory called volatile. What does it mean? Let's imagine that you were working on a computer with some document, saved it, and then, of course, turned off the computer. If HDD memory were volatile, then all the information you saved would be irretrievably lost. Why? The thing is that for normal operation of volatile memory, a constantly switched-on power supply is required. It is on this principle that computer RAM works, but memory on hard drives does not, since it is not volatile. For the same reason, this type of memory is the best for storing any information, be it documents, photographs, videos, etc. By the way, the operating system, as a rule, is installed on the hard drive in a section specially designed for this. Of course, all of the above does not mean at all that information is stored on this type of device for decades; on the contrary, it needs to be periodically “cleaned,” that is, unnecessary and redundant information must be removed.

What do the terms HDD, hard drive and hard drive mean?

What does HDD mean? The answer is: HDD is a hard disk drive that uses a magnetic operating principle. The abbreviation from English (hard disk drive) translates as hard drive. You can also add the word magnetic to this abbreviation, which means magnetic.

By the way, why exactly hard? What is a computer hard drive? Why not soft? There are no secrets here either. The thing is that inside this type of device there are special plates. The plates are solid, in fact, this is the explanation of this name. Perhaps we can say a few words about floppy disks, which appeared at about the same time as hard drives. So these floppy disks, namely their magnetic disks, were soft. So everything is logical and natural.

As for the word hard drive, everything is somewhat more complicated. The reason for the appearance of this name, oddly enough, is intertwined with the designation of the real rifle itself. In 1973, the world saw the HDD 3340 model, which had the engineering designation 30-30 (Two modules of 30 MB each). This designation echoed the name of the 30-30 Winchester cartridges. It's simple.

What do these devices look like inside a personal computer?

Now the most popular HDD models have sizes of 2.5 or 3.5 inches. The latter are used in regular PCs, and the 2.5-inch form factor is intended for laptops and portable versions of devices.

The first thing worth saying is that in the world of computer technology everything is improving, and quite quickly, and the situation with our type of device is no exception. As today? Nowadays the most popular HDD models have sizes of 2.5 or 3.5 inches. The latter are used in regular PCs, and the 2.5-inch form factor is intended for laptops and portable versions of devices. In older PCs you can also find disks with other sizes, but they are outdated and are not usually used in modern computers. Which sizes are already outdated? By and large - everything except the above. Previously, HDDs had a format of 8 and 5.25 inches.

Memory capacity of modern hard drives.

For most users, memory size seems to be a key indicator in choosing the most suitable model for use. Speaking about computers in Russian, we can say it bluntly - no one cares about all the technical characteristics (noise, speed) except one. As you may have guessed, this is exactly the amount of information that can fit on a disk. It doesn’t matter that a hard drive can be noisy and slow, the main thing is how much it can fit. This is what worries the vast majority of users. Moreover, many other characteristics do not look so significant in the eyes of ordinary people, but the amount of free space is the main indicator. Of course, there are users who pay attention to noise, power consumption and other secondary characteristics of any hard drive, but they are in the minority.

In general, when choosing memory for your computer, it is worth remembering one trick from manufacturers. When indicating the amount of memory of a device, they round up all values, so the actual amount of memory will be slightly less than indicated on the package. The thing is that manufacturers round the figures in such a way that one kilobyte ends up being 1000 bytes, not 1024. Hence the “error”. Is it possible to somehow fight this? By and large, no, but it can be used, and we tell you how to do it in Russian: try to use this fact (rounding in favor of the manufacturer) to your advantage: bargain with the seller, pointing out the smaller amount of real hard drive memory instead of the declared one. What if you can save money? Buy yourself a cookie)

HDD is a data storage device - a hard magnetic disk drive. “HDD” is an abbreviation for the English phrase Hard Disk Drive. Other names for HDD: hard drive, hard drive, HDD, screw, hard, tin, tin.

What is HDD for?

HDD is used to store information. The information located on the hard drive is called data. The data on the disk is organized using a file system and is represented by files.

HDD is computer memory. Don't confuse it with RAM. The hard drive is non-volatile memory, RAM is volatile.

The hard drive is now the main storage device, and if you have a computer, then you have a screw.

Operating principle of HDD

Hard drives, that is, HDDs, work similarly to a device that everyone has long forgotten about - a “player”, with a rotating disk and a needle for playing music. The conversion elements (read/write heads) used in hard drives are similar to the read/write heads that are used in VCRs and stereo cassette recorders to access information on magnetic media.

Hard drives store information on a rotating metal or glass plate coated with magnetic material. As a rule, the disk consists of several plates connected by a common rod - a spindle. Each plate is something like a vinyl record with a recording that is played by a turntable. Information is usually stored on both sides of the plate.

As the disk spins, an element called the head reads or writes binary data onto the magnetic media. Information is written to the disk using any encoding method, of which there are a great many. The encoding method and recording density are determined by the disk controller.

Without delving further into the description of the operating principle of an HDD, we can say that a hard drive is, in fact, a super player with a bunch (or maybe just one) of gramophone records inside. Although, of course, in terms of the complexity of the device, the player was not lying around with it.

The past and future of HDD

The very first HDD was developed by IBM in the early 70s.

In 1983, with the release of the first IBM PC/XT computer, a hard drive from Seagate Technology appeared in the lives of thousands of newly minted, still wild users. The early hard drive interface, developed by Alan Shugart (founder of Seagate Technology), was the de facto standard for HDDs for many years. Subsequent developments by Seagate formed the basis for the ESDI and IDE interfaces. Shugart also developed the SCSI interface, which is now used in many modern computers.

By the way, Seagate hard drives are now the best-selling in Europe. And who in Russia doesn’t know the famous Barracudas?

The most important direction in the development of hard drive technology has always been to increase their (storage) capacity. Progress in this area is particularly driven by ever-increasing software requirements. Increasing the capacity of drives is possible either by increasing the size of the drives themselves or by increasing the data storage density. The limit for increasing HDD sizes has been reached, the limit for data storage density has not yet been reached. But it won't be long.

Need to know

1. HDD is a complex contraption for storing information

2. The hard drive is short-lived and is unlikely to last more than three years with constant use.

3. It is extremely undesirable to carry a hard drive (somewhere), twirl it in your hands, or even remove it from the computer case. Winchester is very sensitive to vibration!

4. The internal structure of the HDD is very complex. If you once went to a circle of young radio amateurs, this does not mean at all that you can now repair hard drives. Repairing hard drives requires more than just a soldering iron!

5. Those who like to tinker with hardware need to remember that by opening the HDA of the disk, you thereby put an end to both the information and the hard drive itself

6. In terms of storage security, storage media can be arranged in this order (with increasing risk of data loss): head, paper, hard drive. Do not store important information on the HDD! And if you have to, always make backups!

7. If the information on your hard drive is unavailable for some reason, do not try to restore it! Most likely, you will only completely destroy it - it is better to turn to professionals. Data recovery is no big deal!

8. The word “HDD” is a dirty word and is not used in polite society; it characterizes something (to put it mildly) unreliable, short-lived and disgusting

Hard drive, hard drive or just a screw, hard disk, hdd (Hard Disk Drive) - this data storage device has several names and is the main storage device for storing information in all modern computers, laptops and servers. It is on this device that all your photos, videos, music, films are recorded, and the operating system of the computer itself is recorded on it. Nowadays, SSD drives and hybrid SSHD drives are becoming increasingly widespread; we will talk about them and their pros and cons in a separate article.

What kind of discs are there?

In the store today you can find hard drives with different parameters, how do they differ? Let's try to understand the main differences and highlight several characteristics of the drives.

Form factor (size)

The parameter shows the width of the hard drive in inches. The main width is 3.5 inches and 2.5 inches, used in modern computers and laptops, as well as in external portable and stationary drives and network storage.

For a stationary home computer, the standard size is 3.5 inches, in modern cases there are bays for 2.5-inch drives, they are mainly designed for installing an SSD drive; installing a 3.5-inch drive in a computer instead of a 3.5-inch drive does not make much sense , only in very compact cases, such as micro-ATX.

In laptops, on the contrary, saving space is very important and they use 2.5-inch form factors. There are smaller disks - 1.8 inches, 1.3 inches, 0.8 inches, but you won’t find them in modern devices.

Capacity (Why is the disk capacity less than stated?)

A parameter that directly determines how much information we can record and store on our computer or laptop. Manufacturers indicate the capacity at the rate of 1 kilobyte = 1000 bytes, but computers calculate differently 1 KB = 1024 bytes, hence the confusion among users encountering this for the first time and the larger the volume, the greater the difference in the final volume. Nowadays, disk capacity is measured in terabytes, which is more than enough to store a collection of not only photos, but also music and films.

Interface

You will find drives with a SATA connector in all modern devices today. The only difference is the data transfer speed.

ATA aka PATA (IDE)

Disks with this interface are no longer produced or installed in modern devices, but you can find them in older computers. Initially, the interface was called ATA, but after the appearance of the more modern and high-speed SATA in 2003, it was renamed PATA.

The name IDE was coined by WD (Western Digital) in 1986 for marketing reasons when it developed the first version of this connection standard.

SCSI and SAS

Disks with SAS interface are used in server equipment. They replaced the SCSI interface. The average user should only know that they are intended for completely different tasks and are not used in home PCs.

Spindle speed

The number of spindle revolutions (the axis on which the plate or several plates inside the disk rotate). There are several standards; in home computers and laptops, disks with rotation speeds of 5400, 7200 and 10000 rpm are used; on server equipment there are rotation speeds of 15000 rpm. The parameter affects the time of access to information.

There are several more parameters, such as noise level, time between failures, etc. in modern drives, these parameters correspond to standard criteria and do not differ significantly; we will pay attention to them when we compare and select hard drives.

External drives (portable or stationary)

These are already familiar drives, enclosed in an external plastic or metal box in which a control board or even an entire mini-PC on the board is installed. These drives have various outputs, the main connectors are mini-USB, micro-USB, micro-USB 3.0, fireware and others; portable models are powered by a USB connector. Stationary ones have a separate power cable. Modern models of external drives can work over a wireless wi-fi network. Nowadays you can find network storages on sale with several disks in one case, which can be connected into RAID arrays. We will talk separately about all these devices in future articles.

Every computer has a hard drive or, as it is often called, a hard drive, which is the main storage location for all information used by the computer and its user. The hard drive stores the installed operating system, all programs used by the user, and data. The processor takes the information necessary for processing from the hard drive and then writes it back to the media. The amount of information stored on a hard drive depends on its size.

The very first models of hard drives allowed storing up to 10 MB of data on their disks, which was a lot in those days. Nowadays, modern media allows you to store thousands and tens of thousands of megabytes. The memory capacity on modern models is calculated in gigabytes and terabytes. This makes it possible to store a huge amount of films, music, videos, games and other data. A significant increase in the amount of memory on a HDD is associated with the progressive development of computer technology, as a result of which movies, games and other data take up more and more free space.

Design features of hard drives

A modern hard drive consists of several metal disks on which information is recorded. The discs are coated with iron oxide or another special compound that can store the effects of a magnetic field. The number of disks depends on the volume of the media and usually ranges from 1 to 3. Metal disks are ideally even, smooth and balanced, due to which they can rotate at high speed; according to the standard, it can be 5400, 7200 or 10000 rpm.

Special heads move along the disks with the highest positioning accuracy. Each disk has 2 magnetic heads. Reading data from the surface of disks is carried out by installing special magnetoresistive heads; they work depending on how the magnetic field on the surface of the disk changes. Data is transferred to a computer as a result of receiving an analog signal that turns into digital form.

On disks, information is located in tracks located around a circle. To work with data stored on media, magnetic heads move along tracks. The heads are moved using a special solenoid drive. Such heads can access any location on the disk due to their high rotation speed. The heads are located on both sides of the disks, so each of them carries out work on one side and is fully responsible for it.

A sector on a hard drive allows you to store 512 bytes of information, and each track on a hard drive consists of many sectors. The maximum amount of information that can be stored on a hard drive depends on the number of sectors, heads and cylinders. HDDs may have the same number of disks, but their memory capacities will be completely different. This is due to the fact that to increase capacity, it is more convenient to increase the density of sectors on each of the disks than to increase their number, which will lead to a significant increase in the size of the media. The development of computer technology leads to the fact that each PC component becomes smaller in external dimensions, and, on the contrary, the capabilities increase.

There are such concepts as physical and logical disk placement. Physical is how the storage medium is structured inside, and logical is how the computer sees it. In reality, the physical and the logical are completely different. If physically, for example, 3 disks can be installed inside a hard drive, then logically there can be any number of them and of any size; one logical disk can be the size of two or more physical ones and vice versa.

During the production of hard drives, it is almost impossible to avoid damage to sectors or tracks, but they are not used and are not taken into account by the media due to markings.

There are hard drives designed for use in home PCs, and others for use in servers. The latter are subject to significantly greater requirements, because they work with a significant load and must provide high productivity and speed.

Characteristics of hard drives

In order to choose the right hard drive suitable for a specific purpose, you need to understand a large number of characteristics. The first thing you should pay attention to is the form factor. On desktop PCs, 3.5-inch hard drives are installed, and on laptops, 2.5-inch ones. There are also other less common form factors. The second important parameter is the interface through which the device connects to the computer. PCs use various variations of the SATA interface.

One of the important parameters is capacity, which determines the amount of data stored on the device. The rotation speed of the shaft on which the disks are located affects the speed of working with information.

When choosing a hard drive, you should pay attention to the buffer size, which directly affects the speed of the device's processing of information.

Each hard drive makes noise during operation, like any other mechanical device. During operation, noise can cause significant inconvenience, so you need to pay attention to its level when choosing a model suitable for your PC.

If you plan to frequently move the device from one computer to another, then such a parameter as shock resistance is important. The higher it is, the less likely it is to lose information during an impact or damage the hard drive.

While working with information, the disk provides the requested information at a certain speed. This indicator is called “Random Access Time” and the lower it is, the faster the request will be transmitted.

Having an understanding of all the parameters, characteristics and design of modern hard drives, you can quickly select the appropriate hard drive to perform your tasks on your PC.

Hard drive or HDD This is a device that allows you to store information for a long time and is non-volatile. In simple words, a metal box where all your documents, films, operating system and everything else are located. If we draw a life analogy, it is something like a big album. Taking a pencil in your hands, you can draw or write essays. If you don't like something, you can always take an eraser. The point is that while the album is on the shelf, all data remains intact.

There are two important aspects in this case. The first is long-term storage. The second is energy independence. If in the first case everything should be clear from the example with the album, then for the second case I will give some explanations. The bottom line is that a hard drive does not require power to store information, unlike RAM. So you can turn off your computer from the network and know that your data will be safe.

Note: There is a common version of where the slang names for this box came from. Today, a hard drive is often called a hard drive or, for short, a screw. This came from the fact that the first such device had a code similar to cartridges for a Winchester rifle. How true this is is difficult to say, but the version is considered the most realistic.

Let's take a closer look at this box.

If you noticed, I have already mentioned the abbreviation HDD several times and for a reason. The fact is that the technical name of this box is a hard magnetic disk drive or hard (magnetic) disk drive.

But, let's return to the hard drive device. This box is based on magnetic recording technology. And this is how it works. There are round hard drives (they are also often called pancakes) coated with a ferromagnetic material (which can change its magnetic properties). There is a special moving head (consists of two parts), which, in fact, reads and writes data (part of the head for reading, part for writing).

The process itself goes as follows. The disk is constantly spinning at a fairly high speed, and the head moves along the disk and at the right moment either reads data or writes. It is important to note that the head does not touch the disk, as otherwise the coating on the disk could be damaged. When the disk is turned off, the head is in a special zone (parking), again to protect the ferromagnetic coating from damage.

It is worth knowing that the internal mechanism is made in such a way that it would be physically very difficult to damage the surface of the data disk. However, over time, parts of the ferromagnetic surface may become unusable. Here, as in the famous expression - “Nothing lasts forever.”

It is also worth knowing that there may be several such plates inside the hard drive box. As you probably already guessed, the number of pancakes affects the amount of information stored. But it doesn't stop there. For example, a long time ago, disks were 1.5 times larger than today’s ones, and 20-40 MB were placed on them.

Figure 1. Simplified diagram of a circular hard drive

Note: In the figure the numbers indicate: 1 - geometric sector, 2 - track sector, 3 - track, 4 - cluster.

Let's look at the surface of the pancakes in a little more detail. So that the storage and recording of information can be structured, the entire surface is divided into special tracks. Then the entire disk is divided into geometric sectors (equal to each other). The part of the track that is inside this geometric object is called the track sector or simply sectors. A combination of several sectors is called a cluster.

Since disks spin at a fairly high speed (for example, 7200 rpm), a cluster is used as the minimum storage unit. Typically, a cluster is 4 KB in size and consists of 8 sectors of 512 bytes each. By the way, this is why the actual size of a text file consisting of just one character will be 4 KB, since, in principle, the size is divided precisely by clusters.

Note: It is worth knowing that there are methods that allow you to store data from several files in one cluster, but usually the division is done by clusters.

Note: I also advise you to read the article Solid State Hard Drive or SSD Drive, as this is the next wave of data storage devices.

Hard drive specifications

If the design of hard drives, I hope, has become clear to you, then to complete the picture, it remains to consider the issue of the main characteristics of the HDD.

1. Form factor. The words are scary, but in fact they only mean the physical size of the disk. For desktop computers it is usually 3.5 inches, for laptops it is smaller, only 2.5 inches

2. Capacity. This is essentially the size of how much data a hard drive can store. Today, disks are measured in gigabytes and terrabytes.

3. Spindle speed. This is exactly the speed at which the pancakes spin. Typically this is 5400 for laptops and 7200 for regular computers. There are other speeds, but for home use they are simply not needed.

4. Noise level. Here, you can probably guess what we are talking about. There are very loud hard drives, usually the simplest ones, and there are also quieter ones.

5. Impact resistance or, in common parlance, survivability. Essentially, it indicates how much overload a hard drive can tolerate without damaging data. However, I strongly advise against checking this characteristic.

6. Access interface. The interface defines the connectors that are used to connect drives to the computer. Previously, almost all HDDs for home computers were IDE, but today we are mainly talking about SATA. In the case of external drives, usually USB. It’s worth knowing that in reality the connector of the disk itself is not USB; it’s just that an adapter with a controller is used inside the box.