The computer's hard drive is. Quality characteristics of the hard drive

Greetings to all blog readers. Many people are interested in the question - how does a computer hard drive work. Therefore, I decided to dedicate today's article to this.

A computer hard disk (HDD or hard drive) is needed to store information after the computer is turned off, unlike RAM () - which stores information until the power is turned off (until the computer is turned off).

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

A hard drive is made up of five main parts. And the first of them - integrated circuit, which synchronizes the work of the disk with the computer and manages all processes.

The second part is the electric motor(spindle), causes the disk to rotate at a speed of approximately 7200 rpm, and the integrated circuit keeps the rotation speed constant.

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

But let's still see what happens if the gap disappears and the rocker head comes into contact with 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 huge acceleration becomes incredibly heavy. Given the huge speed of rotation of the disk itself, the weight of the rocker head becomes very, very noticeable. Naturally, disk damage is inevitable in this case. By the way, this is what happened to the disk, in which this gap disappeared for some reason:

The role of the friction force is also important, i.e. its almost complete absence, when the rocker begins to read information, while shifting up to 60 times per second. But wait, where is the engine here that drives the rocker, and even at such a 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. Such interaction allows accelerating the rocker to the speed of light, in the literal sense.

Fourth part- the hard drive itself, this is where information is written and read from, by the way, there may be several of them.

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 housing is often referred to as a "containment zone". There is an opinion that there is no air inside the containment area, or rather, that there is a vacuum there. This opinion is based on the fact that at such high disk rotation speeds, 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 cleaning the air, it was simply pumped out.

We talked about components, i.e. what is a hard drive made of. Now let's talk about data storage.

How and in what form is data stored on a computer hard drive

Data is stored in narrow tracks on the disk surface. During production, more than 200,000 such tracks are applied to the disc. Each of the tracks is divided into sectors.

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

The surface of the disc itself is smooth and shiny, but this is only at first glance. On closer examination, the surface structure turns out to be more complex. 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 a microscopic area on the film (ferromagnetic layer), setting the magnetic moment of such a cell to one of the states: 0 or 1. Each such zero and one are called bits. Thus, any information recorded on a hard disk is, in fact, a certain sequence and a certain number of zeros and ones. For example, a good quality photo occupies about 29 million of these cells, and is scattered across 12 different sectors. Yes, it sounds impressive, but in reality - such a huge number of bits takes up a very small area on the surface of the disk. Each square centimeter of hard disk surface contains several tens of billions of bits.

How a hard drive works

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

So, how a hard drive works next: when the hard drive is put into operation, it means either it is being written to, or information is being read from it, or from it, the electric motor (spindle) starts to gain momentum, and since the hard drives are fixed on the spindle itself, respectively, they are together with it also start to rotate. And until the speed of the disk(s) has reached the level that an air cushion is formed between the rocker head and the disk, the rocker is in a special "parking zone" to avoid damage. Here's what it looks like.

As soon as the speed reaches the desired level, the servo drive (electromagnetic motor) sets in motion the rocker, which is already positioned in the place where you want to write or where to read the information. This is just facilitated by an integrated circuit that controls all movements of the rocker.

There is a widespread opinion, a kind of myth, that at times when the disk is "idle", i.e. no read / write operations are performed with it temporarily, the hard drives inside stop spinning. This is really a myth, because in fact, hard drives inside the case are constantly spinning, even when the hard drive is in power-saving mode and nothing is being written to it.

Well, here we have examined with you the device of the computer hard disk in all details. Of course, within the framework of one article, it is impossible to tell about everything related to hard drives. For example, in this article it was not said about - this is a big topic, I decided to write a separate article about it.

I found an interesting video about how a hard drive works in different modes

Thank you all for your attention, if you have not yet subscribed to updates of this site - I highly recommend doing this so as not to miss interesting and useful materials. See you on the blog pages!

How is a hard drive arranged? What are hard drives? What role do they play in a computer? How do they interact with other components? What parameters to consider when choosing and buying a hard drive, you will learn from this article.

HDD- short name for " Hard Disk Drive". You will also meet English HDD- and slang Winchester or abbreviated Screw.

In a computer, the hard drive is responsible for storing data. The Windows operating system, programs, movies, photos, documents, all the information that you download to your computer is stored on your hard drive. And the information in the computer is the most valuable thing! If the processor or video card fails, they can be bought and replaced. But lost family photos from last summer's vacation or a year's worth of accounting data for a small business are not so easy to recover. Therefore, the reliability of data storage is given special attention.

Why is a rectangular metal box called a disc? To answer this question, we need to look inside and find out how a hard drive works. In the picture below you can see what parts a hard drive consists of and what functions each part performs. Click to enlarge. (Taken from itc.ua)

I also suggest watching an excerpt from the Discovery Channel program about how a hard drive works and works.

Three more facts you need to know about hard drives.

1. The hard drive is the slowest part of a computer. When the computer freezes, pay attention to the hard drive activity indicator. If it blinks frequently or stays on, then the hard drive is executing the commands of one of the programs, while all the others are idle, waiting for their turn. If the operating system does not have enough high-speed RAM to run the program, it uses hard disk space, which greatly slows down the entire computer. Therefore, one way to increase the speed of your computer is to increase the amount of RAM.
2. The hard drive is also the most fragile part of a computer. As you learned from the video, the engine spins the disk up to several thousand revolutions per minute. In this case, the magnetic heads "hover" above the disk in the air flow created by the rotating disk. The distance between the disk and heads in modern devices is about 10 nm. If the disk is subjected to shock or shock at this point, the head may touch the disk and damage the surface with data stored on it. As a result, the so-called bad blocks"- unreadable areas, due to which the computer cannot read any file or boot the system. In the off state, the heads "park" outside the working area and overload from impact is not so terrible for the hard drive. Please make backup copies of important data !
3. The capacity of the hard drive is often slightly smaller than what the seller or manufacturer specifies. The reason is that manufacturers indicate the size of the disk based on the fact that there are 1,000,000,000 bytes in one gigabyte, while there are 1,073,741,824 of them.

Buying a hard drive

If you decide to increase the amount of information storage in your computer by connecting an additional hard drive or replacing the old one with a larger one, what do you need to know when buying?

First, look under the cover of your computer's system unit. You need to find out which hard drive interface the motherboard supports. By far the most widely used standards SATA and outliving its age IDE. They are easy to distinguish by their appearance. The picture on the left shows a fragment of the motherboard, which is equipped with both types of connectors, but yours will most likely be one of them.

There are three versions of the interface SATA. They differ in data transfer speed. SATA, SATA II and SATA III at speeds of 1.5, 3 and 6 gigabytes per second, respectively. All interface versions SATA look the same and are compatible with each other. You can connect them in any combination, as a result, the data transfer rate will be limited to the slower version. At the same time, the speed of the hard drive is even slower. Therefore, the potential of fast interfaces can be revealed only with the advent of new high-speed drives.

If you decide to purchase an additional SATA hard drive, check if you have an interface cable as shown in the picture. It is not sold with a CD. (They are usually bundled with the motherboard.) Also, among the power supply connectors, there should be at least one free one for connecting a hard drive, or you may need an adapter from the old standard to the new one.

Now about the hard drive itself: The main parameter is, of course, the capacity. As I mentioned above, please note that it will be slightly less than stated. The operating system and programs require 100 - 200 gigabytes, which is quite a bit by modern standards. How much additional space you may need, you can determine empirically. Large volumes may be required, for example, to record high quality video. Modern films in HD format reach several tens of gigabytes.

In addition, among the main parameters indicate:

1. Form Factor- disk size. 1.8" and 2.5" disks are used in . For a desktop computer, you should purchase a 3.5-inch drive. They have the same SATA connectors and a laptop drive can work in a desktop computer. But small drives are made with an emphasis on compactness and low power consumption, and are inferior to larger models in terms of speed. And they cost more.
2. RPM- disk rotation speed. Measured in revolutions per minute ( RPM- short for revolutions per minute). The faster the rotation speed, the faster the disk writes and reads information. But it also consumes more energy. Today, the most common discs with 5400RPM and 7200RPM. Lower RPMs are more common in laptop drives, high capacity drives (greater than two terabytes), and so-called "green" drives, named for their reduced power consumption. There are also hard drives with a rotational speed 10000RPM and 15000RPM. They are designed to work in highly loaded servers and have an increased reliability resource, but they also cost much more than conventional ones.
3. Manufacturer. At the moment, there are several large manufacturers on the storage market. Among them there is quite tough competition, so they are in no way inferior to each other in quality. Therefore, you can choose any of the well-known names: Hitachi, HP, Seagate, Silicon Power, Toshiba Transcend, Western Digital.

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 on the market today? How to choose the best device in terms of solving typical user tasks?

What is a hard drive?

The hard drive is the primary storage device for files 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 technology lovers, it is called "hard drive", "screw", "hard". The specifics of hard drives operation is that the read and write heads do not come into contact with the magnetic platter at the same time. Due to this, as well as a number of other design features, the device operates for a long time and can be considered as one of the most reliable means for storing information.

A hard drive is a resource on which, as a rule, system files are located, that is, those that are present in the structure of the OS, various applications, games. Software installation almost always involves the use of "hard drive" resources.

Most modern computer models support multiple hard drives. Laptops most often contain only one hard drive due to the small dimensions of the corresponding devices. Moreover, if we are talking about the type (we will consider 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 the computer. Our task is to determine the criteria for the optimal selection of the appropriate device for a PC. To solve it, it will be useful to first investigate the classification of "hard drives".

Hard disk classification

Consider, therefore, in what varieties modern hard drives are presented on the computer equipment 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 of "hard drives" with a PC 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 speed of revolutions of such devices is much higher - about 15,000 rotations per minute. Server "hard drives" are connected to the main hardware components most often through the 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: computers on which such drives are installed are designed to serve key areas of the digital infrastructure of companies, government organizations, and Internet providers.

The specified types of "hard drives" are to be installed inside the PC or server system unit. But there are also external hard drives. They connect to one of the computer's external ports - most often USB or FireWire. Their functionality is generally similar to that which characterizes internal type devices. The volume of a hard drive that belongs to the category of external ones 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 hard drive for a laptop is most often 4200 or 5400 rpm. Such hard drives usually operate when using the SATA interface. 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 varieties 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 disk 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 specifically with solid state drives. This type of 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 - less weight. Regarding speed, it can be noted that a typical figure for solid-state hard drives is 300-400 Mb / s, which is very decent against the background of the leading communication standards supported by modern computers.

Interfaces

Successful installation of a hard drive in a PC largely depends on the availability of the necessary interfaces in it. Consider the specifics of the most common communication standards in the modern computer technology market. This will be useful for correlating user tasks and the type of "hard drive" that is best suited for solving them.

Among the most common interfaces for connecting external hard drives is USB. At the same time, this communication standard can be presented in different versions - 1, 2 and 3. The speed of a hard disk directly depends on its compatibility with the corresponding technology. Regarding the 1st version of the interface, we can say that when using it, data transfer is possible at 12 Mbps, the 2nd guarantees file exchange at speeds up to 480 Mbps, the 3rd generation of USB interfaces provides an indicator of 5 Gbps. 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 the 2nd version, and even better in the 3rd.

An external computer hard drive can also be connected using the FireWire interface. It is characterized by a high data transfer rate - about 400 Mbps. Extremely effective when working with video files.

Consider the standards used when installing internal type drives in a PC. Considered relatively obsolete, but still a popular interface is the IDE.

It can transfer data at a speed of about 133 Mb / s. It is 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 / s. It is characterized by increased protection against interference. It is actively used in laptops - due to the relatively small size of the connector, as well as a good data transfer rate.

The SCSI interface, as we noted above, is installed mainly on servers. It is also characterized by a high data transfer rate - about 320 Mb / s. 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 Gb / s.

Hard Drive Selection Criteria

The characteristics of the interfaces we have 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, form factor. But the most important characteristic in terms of choosing the optimal device model is the hard disk 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 a PC. It happens that the computer hard drive is incredibly technological, but the support for the relevant standards on the PC motherboard is insufficient. Consider the key nuances of the compatibility of "hard drives" and some hardware components of modern computers.

Size compatibility is important

Above, we noted that hard drives vary in size. It may seem that this parameter is secondary. 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 ​​\u200b\u200ba laptop will be extremely difficult if the size of the drive is too small, and therefore not optimal 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 the placement of 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 hard drives for a laptop, 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 installed.

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 the versions of data exchange standards. So, there are three varieties. It is important that the appropriate communication standard supported by the drive is also compatible with the 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 owner of a PC, therefore, can significantly overpay.

The same applies to the correlation supported by the "hard drive" and PC USB standards. If the hard drive is designed to be connected via USB 3.0 interface, and 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 basically compatible with it. This communication standard is typical for laptops, but is absent from many "desktop" PCs. Of course, FireWire-enabled hard drives are usually compatible with USB interfaces at the same time, and it's 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 such a device as a hard drive is a very subjective parameter. For many users, relatively speaking, several gigabytes of disk space is enough - for example, if they work mainly with documents. For some, a terabyte hard drive will seem insufficiently spacious due to the frequent placement of large amounts of multimedia content on it - videos, photos, music.

It is quite difficult to recommend the optimal amount of storage. But the concept of "more is better" is not always the best option, again from an economic point of view. You can spend money on an expensive, capacious hard drive - 1TB. A whole terabyte will thus be available - but in practice it can hardly be used by half. At the same time, when buying a less capacious, but cheaper drive, the released funds 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 professionals, a 500 GB hard drive is the best solution for most user tasks. So, on a "hard drive" of the appropriate size, you can place about 100-150 thousand photos in good quality, install about 100-150 modern games. If the owner of a PC is not a collector of photographic masterpieces and not a gamer, then it is unlikely that he will use at least half of the corresponding resource. But if he, in turn, is fond of photography and games, then the opportunities that a 500 GB hard drive will give him may really not be enough. At the same time, this volume of the "hard drive" is considered as one of the optimal ones in terms of typical tasks that modern users solve.

Turnover speed

Another important parameter that characterizes a hard drive is the platter rotation speed. Regarding it, we can say that it is important in terms of the actual data transfer rate, as well as the dynamics of the processing of various files by the operating system. If the "hard drive" is used as the main one, that is, it has an OS 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 that is primarily intended for file storage, then in this sense, the speed of rotation of the plates is not the most important indicator.

The higher the value of this indicator, the more expensive the drive. In this sense, overpaying for higher turnovers when they are not required may, again, be undesirable. A "Winchester" with a high disk rotation speed produces significantly more noise than one with a more modest speed, and is also characterized by high power consumption. The optimal rate for modern hard drives, which can effectively solve most user tasks - 7200 rpm.

Cache

Among the significant indicators of drive performance is cache memory. Using this resource, the hard drive can significantly speed up the procedures for performing many file operations. The most frequent request algorithms for certain computer resources are fixed in the cache memory. If some data is present in the cache, then the "hard drive" does not need to look for them in the RAM space or among the files. The larger the cache, the better. But the optimal value of the corresponding indicator recommended by many experts is 64 MB.

Does the brand matter?

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

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 that the corresponding indicator be smaller than the slots provided for hard drives, it is unacceptable that it be larger);

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

Volume (subjectively, but 500 GB is the best indicator for most user tasks);

The speed of rotation of the plates (optimally - 7200 rpm);

Cache memory (optimally - 64 MB).

It is also desirable that the “hard drive” be released by a manufacturer that is in a leading position in the world market in the corresponding segment of devices.

Many have heard words like HDD , « HDD», « screw" or " Winchester". All these words are synonyms for the same device. HDD - This is a device for storing and storing information, which is based on the principles of magnetic recording. The hard drive in most modern computers is the main data storage device. It retains information even when the computer is turned off, it can also be removed from the computer's system unit and connected to another PC .

The history of the hard drive Main difference hard drive from diskettes - this is the recording of information on hard plates (aluminum or glass) coated with a ferromagnetic material, in most cases chromium dioxide. Winchesters are most often used as non-removable storage medium , but in recent years has been invented removable hard drive , which has been widely used. The hard drive is usually combined with a drive, a drive and an electronics unit.

For the first time in the computer market "screw" appeared back in 1957. He was born thanks to the company IBM long before the advent of the personal computer. It was capable of holding 5 MB of information and cost crazy money. A little later, 10 was developed MB hard drive, but for PC. Winchester consisted of 30 tracks and 30 sectors each. After marking "30/30" of the brand of the same name with the popular carbine " Winchester» the drive was named colloquially « Winchester” or abbreviated “screw”. On the territory of Europe and the USA, this term disappeared back in the 90s, and only in Russia it continues to be called in this way in slang.

Winchester consists of several metal discs coated with a special substance that can store a magnetic field. The number of metal plates in a hard drive varies from one to three. These discs have a very smooth surface and excellent balance. These qualities are necessary for high rotation speed. Special magnetic heads, located one at a time on different sides of the discs, allow you to record on them. heads have magnetoresistive properties that are sensitive to changes in the magnetic field through changes in the strength of the current excited in the head. The received signal is read and then digitized. Herself head under the influence of current pulses, it is capable of creating a magnetic field. Depending on the direction of the magnetic moment, sections of the disk are magnetized.

Data on disks is stored in so-called tracks. In the course of the hard drive, the magnetic heads change their location from one track to another. In modern HDD used to change the position of the magnetic heads solenoid drive unit.

A track consists of sectors, each of which stores 512 bytes of data. The smallest disk space is a sector. The product of cylinders, sectors and the number of heads is the maximum volume that can be stored on a hard drive. Almost all manufacturers strive to make tracks as dense as possible and reduce the number of discs.

During work hard drive bad sectors and tracks appear. During low-level formatting, they are specially marked and are not taken into account in the future when the hard drive is working.

Basic parameters of the hard disk

Main characteristic hard drive is an capacity(the amount of information that can be contained). Capacity is measured in gigabytes ( GB). One GB equals 1000 megabytes ( MB). In turn, 1MB is equal to 1000 kilobytes ( KB). But in the information world, a slightly different system of counting has been adopted. Instead of 1000, they count 1024. You need to pay attention to this. When diagnosing a computer, the operating system will indicate fewer GB than specified by the manufacturer.

Another important characteristic is the spindle speed. This indicator directly affects the speed of the hard drive (that is, how quickly information will be exchanged with other computer devices). The higher the rotation speed, the faster the reading and writing of hard disk information. For desktop computers, a good indicator is considered 7200 rpm . At higher rotation rates, the speed of the hard drive increases significantly.

Another important parameter is the random access time, which is closely related to the rotation speed. Most manufacturers do not list this indicator in sales, but if you dig around on the Internet, such information can be easily found. The random access time shows how long the hard drive will read or write information on any of the sections of the disk. This parameter is measured in milliseconds. The lower the indicator, the higher the speed of the hard drive.

It is important to know what interface is equipped with " screw". In simple words, the hard drive connector with which it is attached to the motherboard. Was earlier IDE but now it has been replaced SATA. The latter are equipped with all modern hard disks , they are faster and more convenient to install. It is necessary to consider what interface the motherboard is equipped with. If the connectors do not match, connection will not be possible.

There are also disks specifically for servers. They are the same size as normal HDD, but much faster at work. The rotation speed of such devices reaches 15,000 rpm. They are more reliable than desktop hard drives. Server drives come with a serial interface SAS and SATA and parallel SCSI.

Not so long ago, external hard drives were invented. They are very convenient to use, have a smaller size and weight, large amounts of data. They are also called mobile media or "big flash drive". With the help of external HDD It is convenient to transfer various information in the form of audio recordings, office archives and multimedia files. The controllers are capable of supporting USB 2.0, 3.0 and FireWire.

The average rotation speed of hard drives for laptops is 5400 rpm or 4200 rpm. Also, they must be impact resistant.

Main connection interfaces

USB– serial data transmission. Bandwidth USB 1.1 - 12 MB / s, USB 2.0 - 480 MB / s USB 3.0 - 5 GB / s.

IDE– data transmission is parallel. Bandwidth approximately 133 MB/s. This interface is commonly used in desktop computers and laptops.

SATA – parallel data transfer. The throughput is about 300 MB/s. The main competitor of the IDE. SATA is more resistant to interference and slightly better than IDE.

SCSI– parallel data transfer. It is mainly used when working with servers. It is distinguished by high performance and reliability.

Serial Attached SCSI (SAS)– serial transmission of information. Improved version of SCSI with improved performance and reliability.

firewire- sequential transmission. The speed is close to 400 MB/s. For working with video files, this is the best choice.

Manufacturers

At the end of the last century, there were many manufacturing companies on the computer market. hard drives . But at the moment the number of firms has decreased markedly. Some could not stand the competition, others were bought by more powerful competitors, others began to manufacture products other than hard drives.

In the mid-90s, hard drives were produced by the company Conner Peripherals, later acquired Seagate, and Micropolis. The last one did high qualitySCSI premium drives for servers. The company produced very expensive products, but due to the supply of low-quality spindle bearings, the company suffered huge losses on the return and replacement of hard drives, and subsequently went bankrupt. It was also bought out by Seagate.

Popular and now the products of the Japanese company Fujitsu. Now she is betting on the production of hard drives for laptops and SCSI drives. But it is no longer the same turnover as it was in the last century. In 2001, the firm suffered a serious setback. In that year, the controller chip massively failed, as a result, the company suffered serious financial losses, after which it has not yet recovered. But before the breakdown, the Japanese company was considered a leader in the production of hard drives. Winchesters of this manufacturer were distinguished by excellent characteristics of rotating surfaces. In 2009 mass production of hard drives Fujitsu moved to Toshiba .

Until the beginning of 2000, the disks of the IBM division were considered reference. But after mass failures from drives for PC due to oxidation of the contacts of the german bank connector, the American branch suffered significant financial losses, and was sold Hitachi.

Quantrum left a bright mark on history, but due to massive breakdowns HDD in series SH, she also dropped out of the computer market.

Maxtor was considered the leader in its field. In early 2001, she buys out the division Quantrum, which is engaged in the production of hard drives and inherits a train of problems of the acquired company due to "thin" drives. In 2006, it merged with the company Seagate .

Spring 2011 was the last for Hitachi,very popular in the market hard drives . She's acquired western digital, and in the same year, Samsung's HDD division was taken over by Seagate.

Now there are only three manufacturers left on the hard drive market - Seagate, Western Digital and Toshiba . But recently, due to the development of SSD technology and the emergence of external hard drives, the number of companies ready to offer new technologies and developments begins to increase again.

HDD

Schematic diagram of a hard disk drive.

Hard disk drive, HDD, HDD, Winchester(English) Hard (Magnetic) Disk Drive, HDD, HMDD ; colloquially screw, hard, harddisk listen)) is a non-volatile, rewritable computer storage device. It is the main data storage device in almost all modern computers.

Unlike a "flexible" disk (floppy disk), information in a hard drive is recorded on hard (aluminum or glass) plates coated with a layer of ferromagnetic material, most often chromium dioxide. The HDD uses from one to several plates on the same axis. The reading heads in the operating mode do not touch the surface of the plates due to the layer of the oncoming air flow formed near the surface during rapid rotation. The distance between the head and the disk is several nanometers (in modern disks 5-10 nm), and the absence of mechanical contact ensures a long service life of the device. In the absence of rotation of the disks, the heads are at the spindle or outside the disk in a safe zone, where their abnormal contact with the surface of the disks is excluded.

Name "Winchester"

According to one version, the name “hard drive” was given to the drive thanks to the company in 1973, which released the model 3340 hard drive, which for the first time combined disk platters and reading heads in one all-in-one case. During its development, engineers used the short internal name "30-30", which meant two modules (in the maximum layout) of 30 MB each. Kenneth Haughton, project leader, in consonance with the designation of the popular hunting rifle "Winchester 30-30" suggested calling this disc "Winchester".

Physical size (form factor)(English) dimension) - almost all modern (-2008) drives for personal computers and servers are either 3.5 or 2.5 inches in size. The latter are more commonly used in laptops. The formats - 1.8 inches, 1.3 inches, 1 inch and 0.85 inches - have also become widespread. The production of drives in the form factors of 8 and 5.25 inches has been discontinued.

Random access time(English) random access time) - the time during which the hard drive is guaranteed to perform a read or write operation on any part of the magnetic disk. The range of this parameter is small from 2.5 to 16 ms, as a rule, server disks have the minimum time (for example, Hitachi Ultrastar 15K147 - 3.7 ms), the largest of the current ones are disks for portable devices (Seagate Momentus 5400.3 - 12, 5 ).

Spindle speed(English) spindle speed) is the number of spindle revolutions per minute. Access time and data transfer rate largely depend on this parameter. Currently, hard drives are produced with the following standard rotation speeds: 4200, 5400 and 7200 (laptops), 7200 and 10,000 (personal computers), 10,000 and 15,000 rpm (servers and high-performance workstations).

The block of heads is a package of levers made of springy steel (a pair for each disk). At one end they are fixed on the axis near the edge of the disk. Heads are fixed at the other ends (above the disks).

Disks (plates) are usually made of a metal alloy. Although there have been attempts to make them from plastic and even glass, such plates have proven to be brittle and short-lived. Both planes of the plates, like a tape, are covered with the finest dust of a ferromagnet - oxides of iron, manganese and other metals. The exact composition and application technology are kept secret. Most budget devices contain 1 or 2 platters, but there are models with more platters.

The discs are rigidly fixed on the spindle. During operation, the spindle rotates at a speed of several thousand revolutions per minute (4200, 5400, 7200, 10,000, 15,000). At this speed, a powerful air flow is created near the surface of the plate, which lifts the heads and makes them float above the surface of the plate. The shape of the heads is calculated in such a way as to ensure the optimum distance from the insert during operation. While the disks have not accelerated to the speed necessary for the “take-off” of the heads, the parking device keeps the heads in the parking zone. This prevents damage to the heads and the working surface of the inserts.

The head positioner consists of a stationary pair of strong, usually neodymium, permanent magnets and a coil on a moving head assembly.

Contrary to popular belief, there is no vacuum inside the containment. Some manufacturers make it airtight (hence the name) and fill it with purified and dried air or neutral gases, in particular nitrogen; and a thin metal or plastic membrane is installed to equalize the pressure. (In this case, a small pocket is provided inside the hard drive case for a bag of silica gel, which absorbs water vapor remaining inside the case after it is sealed). Other manufacturers equalize pressure through a small orifice with a filter capable of trapping very fine (several micrometers) particles. However, in this case, the humidity is also equalized, and harmful gases can also penetrate. Pressure equalization is necessary to prevent deformation of the containment housing due to changes in atmospheric pressure and temperature, as well as when the device warms up during operation.

Dust particles that ended up in the containment area during assembly and fell on the surface of the disk are carried off during rotation to another filter - a dust collector.

Low level formatting

At the final stage of assembly of the device, the surfaces of the plates are formatted - tracks and sectors are formed on them.

Early "hard drives" (like floppy disks) contained the same number of sectors on all tracks. On the plates of modern "hard drives" the tracks are grouped into several zones. All tracks of one zone have the same number of sectors. However, there are more sectors on each track of the outer zone, and the closer the zone is to the center, the fewer sectors there are on each track of the zone. This makes it possible to achieve a more uniform recording density and, as a result, an increase in the wafer capacity without changing the production technology.

The zone boundaries and the number of sectors per track for each zone are stored in the ROM of the electronics unit.

In addition, in reality, there are additional spare sectors on each track. If an unrecoverable error occurs in any sector, then this sector can be replaced by a reserve one. remapping). Of course, the data stored in it is likely to be lost, but the capacity of the disk will not decrease. There are two reassignment tables: one is filled in at the factory, the other during operation.

Sector mapping tables are also stored in the ROM of the electronics unit.

During the operations of accessing the "hard drive", the electronics unit independently determines which physical sector should be accessed and where it is located (taking into account zones and reassignments). Therefore, from the external interface, the "hard drive" looks homogeneous.

In connection with the above, there is a very tenacious legend that adjusting the remapping tables and zones can increase the capacity of a hard disk. There are a lot of utilities for this, but in practice it turns out that if the increase can be achieved, then it is insignificant. Modern discs are so cheap that such an adjustment is not worth the effort or time spent on it.

Electronics block

In early hard drives, the control logic was placed on the MFM or RLL computer controller, and the electronics board contained only analog processing modules and control of the spindle motor, positioner and head switch. The increase in data transfer rates forced developers to reduce the length of the analog path to the limit, and in modern hard drives, the electronics unit usually contains: a control unit, read-only memory (ROM), buffer memory, an interface unit and a digital signal processing unit.

The interface box interfaces the hard drive electronics with the rest of the system.

The control unit is a control system that receives electrical signals for positioning the heads and generates control actions for a voice coil drive, switching information flows from various heads, and controlling the operation of all other nodes (for example, spindle speed control).

The ROM unit stores control programs for control units and digital signal processing, as well as service information of the hard drive.

Buffer memory smooths out the speed difference between the interface part and the drive (high-speed static memory is used). Increasing the size of the buffer memory in some cases allows you to increase the speed of the drive.

The digital signal processing unit cleans the read analog signal and decodes it (extraction of digital information). For digital processing, various methods are used, for example, the PRML method (Partial Response Maximum Likelihood - the maximum likelihood with an incomplete response). The received signal is compared with the samples. In this case, a sample is selected that is most similar in shape and temporal characteristics to the decoded signal.

Data recording technologies

The principle of operation of hard drives is similar to the operation of tape recorders. The working surface of the disk moves relative to the reading head (for example, in the form of an inductor with a gap in the magnetic circuit). When an alternating electric current is applied (during recording) to the head coil, the resulting alternating magnetic field from the head gap affects the ferromagnet of the disk surface and changes the direction of the domain magnetization vector depending on the signal strength. When reading, the movement of the domains at the head gap leads to a change in the magnetic flux in the magnetic circuit of the head, which leads to the appearance of an alternating electrical signal in the coil due to the effect of electromagnetic induction.

Recently, the magnetoresistive effect has been used for reading, and magnetoresistive heads have been used in disks. In them, a change in the magnetic field leads to a change in resistance, depending on the change in the strength of the magnetic field. Such heads make it possible to increase the probability of information reading reliability (especially at high information recording densities).

Parallel Write Method

At the moment, it is still the most common technology for recording information on a hard drive. Bits of information are recorded using a small head, which, passing over the surface of a rotating disk, magnetizes billions of horizontal discrete regions - domains. Each of these areas is a logical zero or one, depending on the magnetization.

The maximum achievable recording density using this method is about 23 Gb/cm². Currently, this method is gradually being replaced by the perpendicular recording method.

Perpendicular recording method

The perpendicular recording method is a technique in which bits of information are stored in vertical domains. This allows you to use stronger magnetic fields and reduce the area of ​​material required to record 1 bit. The recording density of modern samples is 15-23 Gb / cm², in the future it is planned to increase the density to 60-75 Gb / cm².

Hard drives with perpendicular recording have been on the market since 2005.

Thermal magnetic recording method

Thermal magnetic recording method Heat-assisted magnetic recording, HAMR ) is currently the most promising of the existing ones, now it is being actively developed. This method uses spot heating of the disk, which allows the head to magnetize very small areas of its surface. After the disk cools, the magnetization "fixes". Railways of this type are not yet represented on the market (as of 2009), there are only experimental samples, but their density already exceeds 150 Gbit / cm². The development of HAMR technologies has been going on for quite some time, but experts still disagree on the maximum recording density. So, Hitachi calls a limit of 2.3-3.1 Tb / cm², and representatives of Seagate Technology suggest that they will be able to bring the recording density of HAMR media up to 7.75 Tb / cm². Widespread adoption of this technology should be expected after 2010.

Interface Comparison