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 file system and are files.

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

The hard drive is now the main information storage device, and if you have a computer, then you also 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 some 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 demands software. 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 an increasing risk of data loss): head, paper, hard drive. Do not store important information on the HDD! And if you have to, do it constantly backup!

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

The hard drive, or hard drive, is the main and very important part of the computer. It stores not only operating system, which controls the computer, but also all the information of a client or several clients. It often happens that the value of information many times exceeds not only the cost of the hard drive, but also the computer as a whole. Therefore, the security of information largely depends on the quality and reliability of such a drive. A modern hard drive looks like the one shown in the picture.

What is a hard drive?

So, what exactly is a storage device, the performance of which determines the well-being and good mood of its owner? In fact, a hard drive is a high-tech equipment that stores digital information even when the computer is turned off.

To be more precise, a hard drive consists of several magnetic disks onto which information is applied and read using a magnetic head. These heads, together with magnetic disks, are in a vacuum, which allows the drive to operate without the influence of the external environment on the process of writing and reading information.

What types of hard drives are there?

So, we found out that a hard drive is an information storage device for a computer. Now let's figure out what types of HDD there are. First of all, it should be noted that hard drives can be divided into two categories:

• External drives that can be connected to any computer via a USB interface. In some ways they resemble a flash drive, only larger in size. Such hard drives do not need special software.
• Internal HDD drives are installed inside computers and have specific connectors for both power and information transfer.

Internal HDDs are also divided into several categories. There are several criteria by which a hard drive can be classified. This is the physical size of the hard drive. There are three standard sizes:

• 5.5 inches. Typically, hard drives of this size are used in desktop computers where there is a lot of free space.
• 3.5 inches are used mainly in laptops where space is limited and large amounts of memory are needed.
• 2.5 inches are used in ultrabooks where space is very limited.

Another feature by which drives are classified is the data exchange protocol between the hard drive and the computer. What protocols can the hard drive use? They are as follows:

• IDE- old version protocol, which was used mainly on computers and laptops before 2000.
• SCSI is a contemporary of IDE, a faster version of drive management, which was used mainly in server machines. It required special drivers to use such hard drives.
• SATA is a modern version of the protocol, which has several variants and has a high speed of writing and reading information. Used in almost all modern computer systems.

Hard drive problems

One of the most frightening messages that can be seen on the screen is that the computer cannot see the hard drive. Why is this so scary for computer users? With such a malfunction, the device does not load the operating system, and accordingly, practically no actions provided for by this system can be performed.

What could cause this problem? The simplest problem leading to this result is a violation of the integrity of the power cables or the system interface. Often, dust or dirt getting inside such a connector leads to this malfunction. And most experienced users are not particularly scared when such a message appears, but simply reconnect the power and interface connectors. This inscription may look something like the one shown in the photo above.

Hard drive not visible for BIOS

When such a malfunction occurs, the first thing to determine is whether the problem is physical or software. How to find out? After a message appears that the computer does not see the hard drive, you need to reboot the machine and enter the BIOS. What is BIOS? This is a program that is written into the ROM of the computer's motherboard. It loads even before the operating system and determines the peripheral devices with which it will work motherboard. For BIOS boot you need to press the appropriate key on the keyboard, usually the DEL or F2 button. After entering the BIOS, you can see the following picture.

This photo shows that the BIOS did not detect any hard drives on the computer. In this case, the problem described above could occur, and the computer, being disconnected from the power cable or interface, is invisible to the BIOS. On the other hand, any malfunction in the hard drive control board will lead to such a problem. Moreover, if it is possible to solve this problem, then only in the appropriate service center. It is almost impossible to eliminate it on your own at home.

Windows 7 does not see the hard drive

But there are times when the hard drive is visible to the BIOS, but the operating system does not boot or Windows is constantly rebooting. In what cases does this happen? Then, when working with the operating system, one of the system files was deleted or an error occurred during overwriting and the file is read incorrectly. Physical damage to the hard drive, scratching or chipping of the disk surface may also occur. If one of the system files was located in this location, then the operating system will not be able to read it and will issue, as system administrators say, blue screen death, which prompts you to reboot the system. If the error repeats, it is better to contact system administrator. Sometimes such software errors can be easily fixed without reinstalling the operating system. But it happens that they are fatal, and they can only be corrected with the help of complete reinstallation systems. To solve this kind of problem, system utilities are usually used that deal with the recovery of software errors. What are these programs?

Hard drive software errors

There are quite a lot of programs for recovering software errors, which can be divided into two categories. The first includes utilities that are located inside the system and can be used after the operating system has fully loaded. These are sets of programs for servicing hard drives.

For example, how to maintain a Windows 7 hard drive? You can maintain your drive directly from the program. To do this, just go to “My Computer” and select the disk that we want to service. Click on the "Properties" tab and see the following picture, shown in the photo above.

Hard drive maintenance programs

As you can see in the picture, the user is offered three utilities:

• Check for errors.
• Disk archiving.

Only the first program corrects errors, and the others will simply service this disk. But there are programs that work without an operating system. The advantage of such utilities is that they can maintain the disk even when the operating system does not boot. For example, one of these programs is called FDISK and was developed by Microsoft as a disk maintenance utility before installing the operating system. It is used by experienced users of Norton Disk Doctor computer equipment, and there are actually quite a lot of such programs, so the choice largely depends on the preferences of a particular person. Before installing Windows from a hard drive, it is advisable to service it with a similar program and correct possible errors.

Hard drive recovery

Often, many users are faced with the problem of recovering data from a problematic hard drive. As mentioned above, often the information stored on it is valued much more than the hard drive itself. Therefore, the work of recovering lost data is not only valuable, but also highly paid. Much depends on how the information disappeared. It is important to remember how Windows deletes information from your hard drive.

The operating system does not erase information that the user wants to remove. It simply deletes the hard drive's table of contents, which allows you to find this information. This table of contents is called a FAT table. And if after that the body is hard Windows disk 10 other information was not recorded, it is quite easy to restore it. There are many programs that can do this job. According to many users, one of the best is Acronis Recovery Expert.

Hard Drive Backup

Be that as it may, no user wants to be constantly under the threat that valuable information is in danger. Therefore, efforts are made to minimize risks. What can be done? Backup useful information the hard drive as a whole or hard sector disk helps solve this problem.

What backup methods are there?

• IN manual mode. The user independently chooses what information and when the program will save. Some companies in their own offices prefer to back up data at the end of the work shift. But there is a danger of losing information that has accumulated during the day.
• Backup to automatic mode. At the same time, the program includes how often and what should be copied and saved.
• Creating a mirrored RAID array that stores all the information from the main hard drive in parallel on another hard drive. If the latter fails, you can easily use a mirror.

Selecting a hard drive

While paying great attention to the safety of information, you should not forget about the choice of the hard drive manufacturer, as well as the technical parameters that characterize the quality of this hard drive. If we talk about the brand of the drive manufacturer, then it is worth choosing a more well-known company, although such a hard drive will cost a little more. Some users prefer Seagate.

If we talk about technical parameters, then, all things being equal, it is worth paying attention to the speed of reading and writing information. Sometimes this data will help you make a choice in favor of one or another hard drive.

Let's sum it up

So, a hard drive is a very valuable and important information on the computer. Therefore, you need to put a lot of effort into choosing a high-quality hard drive. You should also take care to regularly maintain your device. In addition, it is important to pay attention to the security of information, if any, on your computer. If you make all these efforts, your hard drive will serve you for a long time, and the information on it will be completely safe. The operation of your device is entirely in your hands, so take all measures to ensure its normal functioning.

Hard drives are among the key components of a PC or laptop. largely depends on the characteristics of these devices. What types of hard drives are available on the market today? How to choose the optimal device from the point of view of solving typical user tasks?

What is a hard drive?

A hard drive is the main file storage device on a PC or laptop. Structurally, it is a rotating magnetic plate with a reading and writing element - a head. In the slang of computer enthusiasts it is called “hard drive”, “screw”, “hard”. The specificity of the functioning of hard drives is that the reading and writing head at the same time does not contact the magnetic plate. Thanks to this, as well as a number of other design features, the device functions for a long time and can be considered one of the most reliable means for storing information.

Hard drive is a resource on which, as a rule, system files, that is, those that are present in the structure of the OS, various applications, games. Installing software almost always involves using hard drive resources.

Most modern computer models support connecting multiple hard drives. Laptops most often have only one hard drive due to the small dimensions of the corresponding devices. Moreover, if we are talking about types (we will look at their specifics a little later), then their maximum number is most often limited by the availability of the corresponding slots on the PC, as well as the performance characteristics of the computer.

So, the hard drive is the most important hardware component of a computer. Our task is to determine the criteria for the optimal selection of the appropriate device for the PC. To solve this problem, it will be useful to first examine the classification of “hard drives”.

Classification of hard drives

Let us therefore consider the types of modern hard drives available on the computer market.

Among the most popular types of devices is a computer hard drive, which corresponds to a 3.5-inch form factor. Such discs have a rotation speed of 5400 or 7200 rpm. Communication between hard drives and PCs is carried out using various interfaces. The most common are IDE and SATA.

There are hard drives adapted for servers. Their size, as a rule, is the same as in a PC, but the rotation speed of such devices is much higher - about 15,000 rotations per minute. “Hard drives” for servers are connected to the main hardware components most often via a SCSI interface, but support for serial SATA or SAS standards is possible. A server hard drive is an extremely reliable device, which is not surprising: the computers on which such drives are installed are designed to serve key areas of the digital infrastructure of companies, government organizations, Internet providers.

The specified types of “hard drives” must be installed inside system unit PC or server. But there are also external hard drives. They connect to one of the external ports of the computer - most often USB or FireWire. Their functionality is generally similar to that of internal type devices. The capacity of a hard drive classified as external is usually quite large - about 500-1000 GB. The fact is that this type of device is often used to move large amounts of data from one computer to another.

There are hard drives adapted for laptops. Their size is smaller than that of hard drives designed for installation in desktop computers - 2.5 inches. The speed of a laptop hard drive is most often 4200 or 5400 rpm. Such hard drives usually operate when the SATA interface is used. They are characterized by high resistance to changes in position, which is quite logical given the specifics of using laptops.

Among the most technologically advanced types of hard drives are solid-state drives. In principle, they can be considered a separate class of devices, since there are no moving plates in their structure. Data in this type of hard drive is written to flash memory. Devices of this type have both advantages and disadvantages.

Many of the world's leading PC manufacturers are adapting their factory lines to produce devices equipped with solid-state drives. This type Hard drives are more expensive than those with rotating elements. However, in comparison with them, they are characterized by reduced power consumption, almost complete absence of noise during operation, and in many cases, lighter weight. Regarding speed, it can be noted that the typical figure for solid-state hard drives is 300-400 MB/sec, which is very decent compared to the leading communication standards supported by modern computers.

Interfaces

The successful installation of a hard drive in a PC largely depends on the presence of the necessary interfaces in it. Let's consider the specifics of the most common communication standards in the modern computer market. This will be useful for correlating the user’s tasks and the type of “hard drive” that is optimal for solving them.

Among the most common interfaces for connecting external hard drives is USB. Moreover, this communication standard can be presented in different versions- 1, 2 and 3. The speed of the hard drive directly depends on its compatibility with the relevant technology. Regarding the 1st version of the interface, we can say that when using it, data transfer at 12 Mbit/s is possible, the 2nd guarantees file exchange at speeds of up to 480 Mbit/s, the 3rd generation of USB interfaces provides a figure of 5 Gbit/s. If you intend to use the device not only for storing files, but also, for example, for installing games or programs, then it is best if it supports the most modern USB interfaces - in version 2, and even better in version 3.

An external computer hard drive can also be connected using the FireWire interface. It is characterized by a high data transfer speed of about 400 Mbit/s. Extremely effective when working with video files.

Let's look at the standards used when installing internal drives in PCs. Considered relatively outdated, but still popular, the interface is IDE.

It can transfer data at a speed of about 133 Mbps. Common in desktop PCs, largely due to the rather large size of the connector, which is not optimal for the structural structure of a laptop.

The SATA interface is the result of improvements to the IDE standard. Allows you to transfer data at speeds up to 300 Mb/sec. Characterized by increased immunity to interference. It is actively used in laptops - due to the relatively small size of the connector, as well as good data transfer speed.

The SCSI interface, as we noted above, is installed mainly on servers. It is also characterized by high data transfer speeds - about 320 Mb/sec. There is a modernized modification of the interface in question - SAS. Hard drives operating when it is activated can provide data exchange at a speed of about 12 Gbit/sec.

Hard drive selection criteria

The characteristics of the interfaces we discussed above can be considered significant criteria when choosing a hard drive. We also announced a number of other important parameters, such as the rotation speed of the device elements and form factor. But probably the most significant characteristic in terms of choosing the optimal device model is hard drive memory. In many ways, this parameter is subjective - many users will prefer a faster hard drive than one that can accommodate a large number of files. However, it is still the first thing that many users pay attention to.

The most important aspect of choosing a hard drive is that some of its nominal characteristics (for example, compatibility with certain interfaces) must be compatible with the communication capabilities of the PC. It happens that the computer hard drive is incredibly technologically advanced, but the support for the corresponding standards on the PC motherboard is insufficient. Let's look at the key nuances of compatibility between hard drives and some hardware components of modern computers.

Size compatibility is important

We noted above that hard drives vary in size. It may seem that this parameter is of secondary importance. But often it turns out to be almost decisive. The fact is that installing a hard drive in a PC or in the corresponding area of ​​a laptop will be extremely difficult if the size of the drive is too small, and therefore suboptimal in terms of using the space available in the structure of the device. It will be practically impossible if the dimensions turn out to be too large - the hard drive simply will not fit into the computer.

Of course, this pattern is typical mainly for laptops, since problems with placing a hard drive in “desktop” PCs usually do not arise (largely due to the availability of various additional devices). Therefore, when planning to purchase new laptop hard drives, you need to know what the exact size of the current ones is. We noted above that “hard drives” with a 2.5-inch form factor are common in the corresponding types of computers. But you need to keep in mind that some laptop models have 1.8-inch hard drives.

Communication standards compatibility

The communication interfaces of the hard drive and the PC motherboard must also be compatible. The main nuance here is the differences in versions of data exchange standards. So, there are three varieties. It is important that the corresponding communication standard supported by the drive is also compatible with motherboard. It may happen that the user buys an expensive hard drive that provides data exchange according to the modern SATA 3 standard (the price of such models can be about 10 thousand rubles), but the computer will not be able to fully support it. The PC owner can thus significantly overpay.

The same applies to the correlation between the USB standards supported by the hard drive and the PC. If the hard drive is designed to be connected via USB 3.0, but the motherboard does not support it, then the technological capabilities of the corresponding standard will also not be fully realized. Regarding the FireWire interface, we can say that when buying a hard drive that supports it (the price of the device can also be decent - about 8-10 thousand rubles), you need to make sure that the PC is, in principle, compatible with it. This communication standard is typical for laptops, but is absent on many desktop PCs. Of course, hard drives that support FireWire are usually also compatible with USB interfaces, and it is extremely unlikely that the device will be non-functional due to the lack of a FireWire port on the PC. But if the user, for example, expected to use the most obvious competitive advantage of FireWire - efficient work with video data, then he may not get the desired results from the hard drive.

Optimal volume

As we noted above, volume as the main characteristic of a device such as a hard drive is a very subjective parameter. For many users, relatively speaking, a few gigabytes of disk space are enough - for example, if they work mainly with documents. For some, a terabyte hard drive will not seem spacious enough due to the frequent placement of large volumes of multimedia content on it - videos, photos, music.

It is quite difficult to recommend the optimal storage capacity. But the concept “the more the merrier” is not always best option, again from an economic point of view. You can spend money on an expensive, spacious hard drive - 1TB. A whole terabyte will thus be available - but in practice it can be used barely half. At the same time, when purchasing a less capacious but cheaper drive, the freed-up financial resources can be used to improve the performance of a PC or laptop (for example, buy an additional RAM module or a more powerful cooler for the processor).

According to a number of IT specialists, a 500 GB hard drive is the optimal solution for most user tasks. So, on a hard drive of the appropriate capacity, you can place about 100-150 thousand photographs in good quality, and install about 100-150 modern games. If the PC owner is not a collector of photo masterpieces or a gamer, then it is unlikely that he will use at least half of the corresponding resource. But if he, in turn, is interested in photography and games, then the opportunities that a 500 GB hard drive will give him may indeed not be enough. At the same time, this hard drive volume is considered one of the optimal ones from the point of view of typical tasks that modern users solve.

RPM speed

Another important parameter that characterizes a hard drive is the platter rotation speed. Regarding it, we can say that it is important from the point of view of the actual data transfer speed, as well as the dynamics of the operating system processing of various files. If the hard drive is used as the main one, that is, the OS is installed on it, programs and games are installed on it, then it is better if the characteristic in question is expressed in as large quantities as possible. If a user buys a second hard drive intended primarily for storing files, then in this sense the rotation speed of the platters is not the most important indicator.

The higher the value of the indicator in question, the more expensive the drive. In this sense, overpaying for higher revolutions, despite the fact that their presence is not required, may, again, turn out to be undesirable. A hard drive with a high disk rotation speed produces significantly more noise than one with a more modest rotation speed, and is also characterized by high power consumption. The optimal indicator for modern hard drives, at which most user tasks can be effectively solved, is 7200 rpm.

Cache memory

Among the significant performance indicators of a drive is cache memory. By using this resource, a hard drive can significantly speed up the procedures for performing many operations with files. The cache memory records the most frequent algorithms for requests to certain computer resources. If some data is present in the cache, then the hard drive does not need to look for it in space RAM or among files. The larger the cache size, the better. But the optimal value of the corresponding indicator recommended by many experts is 64 MB.

Does brand matter?

Does it make sense to choose a hard drive, all other things being equal, based on the brand? The opinions of IT experts and users on this matter are very different. This applies to both the recommendation to focus on the brand and points of view on the quality of drives produced by a particular manufacturer. Some users will characterize their Samsung-manufactured hard drive exclusively positively; reviews from other owners of a device from the Korean brand may be less enthusiastic. Some IT experts praise the brands Hitachi, Toshiba, others do not consider them anything better than competitors. At the same time, these companies are market leaders. In any case, this fact should be considered significant. Becoming a leader in the highly competitive computer components market does not come easy. This probably contributes to high quality manufactured goods.

So, if we need a hard drive for a PC or laptop, then we can focus on the following set of criteria:

Size (relevant mainly for laptops - it is undesirable for the corresponding indicator to be smaller than the slots provided for hard drives; it is unacceptable for it to be larger);

Supported standards (it is important that the technological interfaces on the hard drive are fully compatible with PC resources);

Volume (subjective, but 500 GB is the optimal indicator for most user tasks);

Plate rotation speed (optimally 7200 rpm);

Cache memory (optimally 64 MB).

It is also desirable that the hard drive be produced by a manufacturer that is a leader in the world market in the corresponding device segment.

When the computer starts, a set of firmware stored in BIOS chip, checks equipment. If everything is fine, it transfers control to the operating system boot loader. Then the OS loads and you start using the computer. At the same time, where was the operating system stored before turning on the computer? How did your essay, which you wrote all night, remain intact after the PC was turned off? Again, where is it stored?

Okay, I probably went too far and you all know very well that computer data is stored on the hard drive. However, not everyone knows what it is and how it works, and since you are here, we conclude that we would like to find out. Well, let's find out!

By tradition, let's look at the definition of a hard drive on Wikipedia:

Hard drive (screw, hard drive, hard magnetic disk drive, HDD, HDD, HMDD) - a random access storage device based on the principle of magnetic recording.

Used in the vast majority of computers, and also as separately connected storage devices backup copies data, as file storage, etc.

Let's figure it out a little. I like the term " hard disk drive ". These five words convey the essence. HDD is a device whose purpose is to store data recorded on it for a long time. The basis of HDDs are hard (aluminum) disks with a special coating, onto which information is recorded using special heads.

I will not consider the recording process itself in detail - essentially this is the physics of the last grades of school, and I’m sure you have no desire to delve into this, and that’s not what the article is about at all.

Let us also pay attention to the phrase: “ random access "Which, roughly speaking, means that we (the computer) can read information from any section of the railway at any time.

An important fact is that the HDD memory is not volatile, that is, no matter whether the power is connected or not, the information recorded on the device will not disappear anywhere. This is an important difference between permanent computer memory and temporary memory ().

Looking at a computer hard drive in real life, you will not see either disks or heads, since all this is hidden in a sealed case (hermetic zone). Externally, the hard drive looks like this:

Why does a computer need a hard drive?

Let's look at what a HDD is in a computer, that is, what role it plays in a PC. It is clear that it stores data, but how and what. Here we highlight the following functions of the HDD:

• Storage of OS, user software and their settings;
• Storage of user files: music, videos, images, documents, etc.;
• Using part of the hard disk space to store data that does not fit in RAM (swap file) or storing the contents of RAM while using sleep mode;

As you can see, the computer hard drive is not just a dump of photos, music and videos. The entire operating system is stored on it, and in addition, the hard drive helps cope with the load on the RAM, taking on some of its functions.

What does a hard drive consist of?

We partially mentioned the components of a hard drive, now we will look at this in more detail. So, the main components of the HDD:

• Frame — protects hard drive mechanisms from dust and moisture. As a rule, it is sealed so that moisture and dust do not get inside;
• Discs (pancakes) - plates made of a certain metal alloy, coated on both sides, on which data is recorded. The number of plates can be different - from one (in budget options) to several;
• Engine — on the spindle of which the pancakes are fixed;
• Head block - a design of interconnected levers (rocker arms) and heads. The part of the hard drive that reads and writes information to it. For one pancake, a pair of heads is used, since both the upper and lower parts are working;
• Positioning device (actuator ) - a mechanism that drives the head block. Consists of a pair of permanent neodymium magnets and a coil located at the end of the head block;
• Controller - electronic chip work manager HDD;
• Parking zone - a place inside the hard drive next to the disks or on their inner part, where the heads are lowered (parked) during downtime, so as not to damage the working surface of the pancakes.

This is a simple hard drive device. It was formed many years ago, and no fundamental changes have been made to it for a long time. And we move on.

How does a hard drive work?

After power is supplied to the HDD, the motor, on the spindle of which the pancakes are attached, begins to spin up. Having reached the speed at which a constant flow of air is formed at the surface of the disks, the heads begin to move.

This sequence (first the disks spin up, and then the heads start working) is necessary so that, due to the resulting air flow, the heads float above the plates. Yes, they never touch the surface of the disks, otherwise the latter would be instantly damaged. However, the distance from the surface of the magnetic plates to the heads is so small (~10 nm) that you cannot see it with the naked eye.

After startup, first of all, service information about the state of the hard disk and other necessary information about it, located on the so-called zero track, is read. Only then does work with the data begin.

Information on a computer's hard drive is recorded on tracks, which, in turn, are divided into sectors (like a pizza cut into pieces). To write files, several sectors are combined into a cluster, which is the smallest place where a file can be written.

In addition to this “horizontal” disk partition, there is also a conventional “vertical” partition. Since all the heads are combined, they are always positioned above the same track number, each above its own disk. Thus, during HDD operation, the heads seem to draw a cylinder:

While the HDD is running, it essentially performs two commands: read and write. When it is necessary to execute a write command, the area on the disk where it will be performed is calculated, then the heads are positioned and, in fact, the command is executed. The result is then checked. In addition to writing data directly to the disk, the information also ends up in its cache.

If the controller receives a read command, it first checks whether the required information is in the cache. If it is not there, the coordinates for positioning the heads are calculated again, then the heads are positioned and the data is read.

After completion of work, when the power to the hard drive disappears, the heads are automatically parked in the parking zone.

This is basically how a computer hard drive works. In reality, everything is much more complicated, but the average user most likely does not need such details, so let’s finish this section and move on.

Types of hard drives and their manufacturers

Today, there are actually three main hard drive manufacturers on the market: Western Digital (WD), Toshiba, Seagate. They fully cover the demand for devices of all types and requirements. The remaining companies either went bankrupt, were absorbed by one of the main three, or were repurposed.

If we talk about the types of HDD, they can be divided as follows:

1. For laptops, the main parameter is the device size of 2.5 inches. This allows them to be compactly placed in the laptop case;
2. For PC - in this case it is also possible to use 2.5" hard drives, but as a rule, 3.5" are used;
3. External hard drives are devices that are separately connected to a PC/laptop, most often serving as file storage.

There is also a special type of hard drive - for servers. They are identical to regular PC ones, but may differ in connection interfaces and greater performance.

All other divisions of HDD into types come from their characteristics, so let’s consider them.

Hard drive specifications

So, the main characteristics of a computer hard drive:

• Volume — an indicator of the maximum possible amount of data that can be stored on the disk. The first thing they usually look at when choosing a HDD. This indicator can reach 10 TB, although for a home PC they often choose 500 GB - 1 TB;
• Form factor — size of the hard drive. The most common are 3.5 and 2.5 inches. As mentioned above, 2.5″ in most cases are installed in laptops. They are also used in external HDDs. 3.5″ is installed in PCs and servers. The form factor also affects the volume, since a larger disk can fit more data;
• Spindle speed — at what speed do the pancakes rotate? The most common are 4200, 5400, 7200 and 10000 rpm. This characteristic directly affects the performance, as well as the price of the device. The higher the speed, the greater both values;
• Interface — method (connector type) of connecting the HDD to the computer. The most popular interface for internal hard drives today is SATA (older computers used IDE). External hard drives are usually connected via USB or FireWire. In addition to those listed, there are also such interfaces as SCSI, SAS;
• Buffer volume (cache memory) - a type of fast memory (like RAM) installed on the hard drive controller, designed for temporary storage of data that is most often accessed. The buffer size can be 16, 32 or 64 MB;
• Random access time — the time during which the HDD is guaranteed to write or read from any part of the disk. Ranges from 3 to 15 ms;

In addition to the above characteristics, you can also find such indicators as:

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 that contains all your documents, movies, operating system and everything else. 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 bottom line is that while the album is on the shelf, all data remains untouched.

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, 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 mostly 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.

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