What is the hard drive responsible for? Data recording technologies

When the computer starts, a set of firmware stored in the BIOS chip checks the hardware. If everything is ok, it passes control to the bootloader operating system. 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!

What is a hard drive

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

HDD (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 important difference permanent memory computer, from temporary ().

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 (to budget options), up 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 — an electronic microcircuit that controls the operation of the 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 so simple hard device disk. 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 drive and other necessary information about him, located on the so-called zero track. 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.

Like this in general outline and the computer hard drive is working. In reality, everything is much more complicated, but to the average user, most likely, such details are not needed, so let's finish this section and move on.

Types of hard drives and their manufacturers

Today, there are actually three main manufacturers on the market hard drives: 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 body;
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 disks- 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 ones characteristics of hard computer disk:

• 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 figure can reach 10 TB, although for a home PC they often choose 500 GB - 1 TB;
• Form factor — size of the hard disk. 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 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) HDD connections 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) - type fast memory(type of RAM) hard drive installed on the 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:

Hello, friends! What is a hard drive or HDD? A hard drive is a hard magnetic disk drive. Abbreviated as HDD or hard (magnetic) disk drive - HDD or MHDD. The first hard drive was released by IBM in 1956 and had dimensions of about one cubic meter and was capable of storing up to 3.5 MB of information (see the picture on the left from Wikipedia). It consisted of 50 magnetic disks with a diameter of 610 mm. The surface of the disks was covered with pure iron, which made it possible to magnetize areas and store data. This hard drive weighs 971 kg and was part of the first serial computer IBM 305 RAMAC. Further technology developed and reached what you see in your desktop PCs and laptops. A hard drive is also called a hard drive, a hard drive, or, for short, a screw. The name Winchester comes from the 70s. At that time, IBM released new computer with a more modern hard drive, which consisted of two cabinets, each stored up to 30 MB of information. An analogy was drawn with the Winchester rifle, which used the 30-30 cartridge. Probably after this hard drives, most likely forever (at least among the Russian-speaking population), the name - hard drive or abbreviated - screw - has stuck.

A modern hard drive consists of:

• housing
• electronics unit
• actuator positioning unit
• block with magnetic plates

Let's look at each in more detail

Frame. It's like the body of a car. Everything rests on him. The main task is to provide the necessary rigidity and tightness. Rigidity is necessary to protect the disk from external damage. Tightness - to prevent foreign particles from entering the disk. The case is made of a heat-conducting alloy, since heat is generated during operation of the device and must be dissipated somehow. You can read more about HDD cooling. To equalize the pressures outside and inside the housing, a small window with a flexible metal plate is made.

Electronics unit

Comprises:

• interface block
• buffer or cache
• control unit

The interface unit is responsible for connecting the hard drive to the computer. ROM, a permanent storage device, records service information and disk firmware. Buffer is a cache memory similar to RAM. Frequently used information is placed in it, which increases the performance of the HDD. The cache read speed is approaching the maximum speed for the disk interface. On this moment most common SATA interface III with a maximum throughput of 6 Gbit/s. The control unit is responsible for the functioning of the entire device. It monitors the rotation speed of the block with magnetic plates and the position of the block with actuators.

It consists of an actuator (a device for writing and reading information), a bracket (on which it all works) and a drive. The drive receives commands on where to read and where to write information from the control unit. (The picture below is taken from the site http://www.3dnews.ru/editorial/640707)

Block with memory plates. Consists of a drive, disks or plates and separators. The latter are used to set a certain distance between the plates. Discs with separators are mounted on the drive. The latter maintains a constant rotation speed.

2. How does a hard drive work?

When you turn on the computer, the control unit supplies power to the drive with magnetic disks and waits until the latter reaches the specified rotation speed. As soon as this happens, the computer receives a signal that the HDD is ready. Next comes the request for information. The positioning unit comes into play, which sets the desired position of the actuator. The data is read and goes into the interface block, and from there into the RAM.

Previously, actuators touched magnetic disks. As the speed of the latter increased, a different technology was required. In this case, the actuator hovered above the magnetic surface and touched the disk in a certain place. The technology has moved on, the speed of rotation of the plates has increased and the block with actuators began to be parked outside the plates. That is, the actuators are located next to the plates until the required speed rotation of magnetic disks.

Due to the high speed of rotation of the discs, an air flow is created that lifts the actuator head above the surface. The same air flow blows away dust particles trapped inside from the surface onto a special filter in the housing. There is also an adsorbent in the case to remove residual moisture.

In modern hard drives, the distance between the read head and the surface of the magnetic platinum< 10 нм. Благодаря тому, что считывающие головки никогда не касаются магнитных пластин отсутствует трение и продлевается срок жизни HDD.

Each magnetic plate is divided into ring tracks approximately 60 nm wide. The latter, in turn, are divided into clusters. Typically a cluster is 4 KB. Each bit of information represents a pad on a track that may be magnetized -1 or not -0. These sites are also called domains. How smaller size this site, so more information will fit on the track and a more capacious hard drive will be obtained. At the beginning of development, longitudinal recording was used. The site was located along the path. Later, this technology was replaced by perpendicular recording, which made it possible to increase data density and, in turn, increase HDD capacity.

The set of tracks equidistant from the center of rotation of the engine is called a cylinder.

Before hard drives exceeded the capacity limit of 500 MB, the CHS (cylinder-head-sector) positioning system was sufficient. With the growth in volume, the LBA (linear block addressing) positioning system was adopted in 1994. In the case of CHS, the hard drive was transparent to operating systems, but with linear addressing, the system addresses the desired hard sector disk, and the HDD control unit understands where this sector is physically located.

Actuator positioning unit. Driven by a solenoid motor. The latter consists of a stator and a coil. The stator consists of one or two permanent, strong neodymium magnets. Precise positioning of the bracket with the heads occurs by applying a voltage of a certain force to the coil (picture taken from http://www.3dnews.ru/editorial/640707)

The speed of head positioning and, consequently, the time of access to information depends on the strength of the magnets. The latter in hard drives varies from 3 to 12 ms. The shorter the time, the faster and more expensive the hard drive. WD has three series of hard drives: green, blue and black. The green one uses one neodymium magnet and a spindle speed of 5400 rpm. This results in rather modest performance, but decent efficiency and low power consumption. Blue discs use the same magnet and the rotation speed rises to 7200 rpm. In terms of speed characteristics, it occupies an intermediate position between green and black HDDs. Black ones use two magnets and a speed of 7200 rpm. This allows you to achieve maximum performance. You can increase the performance even higher by increasing the rotation speed of the motor with magnetic plates to 10,000 or 15,000 rpm. These discs have minimum time access to information and are mainly used in servers. Solid State Drives with Access Speed< 1 мс пока остаются вне конкуренции.

Hard drives produce two types of noise when operating. From rapidly rotating magnetic disks and from the impact of the block with heads on the limiter. The latter occurs when the block with heads returns to the parking position. To reduce this impact, manufacturers install rubber linings, but sometimes this does not help, especially on fast wheels. There are two ways to reduce noise from HDD. The first is to make shock-absorbing mounts in the PC case. You can read more about this. The second way is to use AAM technology, which I wrote about in more detail.

3. Hard drive production and manufacturers

In the beginning there were about 70 HDD manufacturers. Thanks to competition, there are only three left. These are Toshiba, Seagate and WD. In the diagram below you can see in which years the acquisitions took place

Production. In the machine shop, blanks are cut from cylindrical aluminum blanks. Then the workpieces are given required form perhaps even on lathes. After the workpiece is delivered to the polishing shop where the surfaces are polished to the required level. Then control takes place and the workpieces are sent to the magnetic coating workshop. Then control occurs again. Then the hard drive is assembled and low-level formatted. In this process, magnetic plates are divided into tracks and checked for broken or unreadable sectors. The latter are immediately marked to prevent the recording of information in them. Each track has a certain reserve of sectors. It is from this reserve that faulty areas discovered during operation are replaced.

Separately, it is necessary to say about the production of heads for reading and writing information. In modern hard drives, each actuator consists of two heads, one for reading and one for writing. The complexity of producing heads is comparable to the complexity of producing processors; photolithography is also used. The design of the heads is a production secret.

Conclusion

In the article we touched on a little history by providing a picture of the first hard drive released in 1956. They said possible reason naming magnetic hard disk drives in a short word - screw. Then we looked at the composition of the hard drive, what is hidden inside its case. We tried to pay attention to each block separately. We examined the operation of the hard drive. In the end, we figured out the manufacturers and the HDD production itself. I hope you have progressed with me in the HDD topic.

Good day to everyone, my dear friends and readers. A friend told me that when he was still working in a video salon, a granny of about 70-80 years old came to see him. She approached a friend and said that she needed “HADEDE”. The friend didn’t seem to understand right away and asked again, “hadede?” She repeated it again, but when she saw that her friend was not smoking, she took out a piece of paper and said that her grandson told her to buy HADEDE.

On that piece of paper it was written HDD 160 GB. Well, the friend grinned and said that it was a hard drive for a computer and directed them to another store. But that’s not what’s surprising anymore. How could a grandson even send his grandmother to get a hard drive? Well, did he fall out of the oak tree?

But what am I getting at? Let me tell you what a HDD is in a computer. Then you definitely won’t have any questions if you want to buy it for yourself.

HDD (Hard Disk Drive) is the hard drive of your computer. You can hear in conversations and alternative names of this device, for example “Winchester”, “Screw”, “Hard”, “Hard”, etc. This device is needed to store your information; in addition, the operating system in which you work is installed on it. Those. Without a hard drive, you can't do much with your computer.

The hard drive is a long-term source of memory and after the power is turned off, all information remains on it, unlike fast RAM. Therefore, you can always store your files, photos, music, etc. on it. But of course this is a device, so don’t forget about it for greater security.

I can already hear the question “Why is it called a hard drive? These are small arms!” Indeed, what could a storage device have in common with a gun? The fact is that in 1973, the well-known company IBM released the hard drive model 3340, but for the sake of harmony they began to call it simply “30-30”, which meant two modules of 30 megabytes each.

Chief Kenneth Haughton found the 30-30 consonance in the famous rifle. The fact is that the cartridges for this rifle had the same marking 30-30, where the first number meant the size of the caliber in inches (0.30 - 7.62 cm), and the second number meant the weight of gunpowder in grains (this is not a typo, but a measure of weight ), which the cartridge was filled with (30 grains is approximately 1.94 grams).

For convenience, it was decided to use this name as slang. True, this slang has not been used by Americans for a long time, but in our country it has not yet gone out of use, although more often it can be heard in the abbreviated name “Screw”.

Hard drive device

Externally, this thing looks like a small rectangular box, but inside it there are several magnetic disks on one spindle, which look somewhat similar to a CD. And of course, there is a certain reading head, which runs along these magnetic plates, reading all the information. Well, of course, there are other components, but I think that these are all details.

And this work is somewhat similar to the work of a record player, only the reader does not have a needle and does not touch the magnetic disks, although the distance between them is simply insignificant.

Basic characteristics of the hard drive

Volume

The capacity of your hard drive determines how much information you can store on it. Over time, memory sizes have increased by new hard increase because there is a real need for it. If on my first computer the volume was 40 GB and that was enough for me, now I have 2000 GB on my computer and I have already used half of it. Of course, some can be removed without tears).

But there is one trick. Manufacturers write the size, for example, 500 GB, but when you connect the hard drive to the computer, you will see a much smaller volume there, about 476 GB. Where did the 24 extra GB go? Yes, it's very simple.

Manufacturers round up the sizes, saying 1 GB is 1000 MB, 1 MB is 1000 KB, etc. It turns out that they are selling you a disk with a capacity of 500 million bytes, and if you divide by 1000, and then by another 1000, you get 500 GB.

But 1 GB is actually not 1000, but 1024 MB, just as 1 MB is not 1000, but 1024 KB. As a result, it turns out that we divide 500 million by 1024, and then by 1024 again and get our 476 GB with kopecks. My 2 terabyte disk consumes about 140 GB. Not bad, right? In general, now you will know.

Rotational speed

The performance of a hard drive is also determined by the spindle speed. And the higher this speed, the greater the disk performance, but the more energy required and the greater the likelihood of failure.

For laptops and external hard drives, the speed of 5400 rpm is most often used, since this is really more expedient for these devices. The speed of information exchange is lower, but there is a lower probability of failure.

On desktop computers in most cases, hard drives are installed with a speed of 7200 rpm. This is really beneficial here, since stationary equipment usually has more powerful equipment that can operate at such a speed. Plus, the computer is constantly connected to the outlet, which means there will be no shortage of energy.

There are also higher numbers of revolutions, even 15,000, but I will not consider them here.

Connection interface

And of course, hard drives are constantly being improved and even their connection connectors are changing. Let's see what connectors there are.

IDE (ATA/PATA) is a so-called parallel interface with a possible data usage speed of up to 133 MB per second. But today this interface is outdated and hard drives with such a connector are no longer produced.

SATA - Serial interface, a more modern one, which replaced the IDE. The standard currently has three different revisions with at different speeds data transfer: SATA 1 - up to 150 MB/s, SATA 2 - up to 300 MB/s, SATA 3, up to 600 MB/s.

USB - This standard refers to external portable hard drives that are connected to a computer via USB and can be used in peace of mind. The advantage of such a device is that you can turn it off at any time without turning off the computer itself.

There are other interfaces, such as SCSI or SAS, but these are no longer mandatory standards for simple use.

Form factor

I was recently asked, what is the form factor of hard drives? Everything is simple here. These are just its dimensions. There are 2.5 and 3.5 inches. There are others, of course, but they are Everyday life no one uses them or they are long outdated.

A 2.5" HDD will be inserted into laptops, and a 3.5" HDD into desktop computers. I think you won't confuse anything)

Well, that seems to be all I wanted to tell you in this article. But I can already hear: “Why didn’t you tell me about the SSD?” My friends, a separate article needs to be written about SSDs, especially since this type is a high-speed solid-state drive. In general, I will definitely write about him).

Best regards, Dmitry Kostin.

Hard drives, or, as they are also called, hard drives, are one of the most important components computer system. Everyone knows about this. But not every modern user even has a basic understanding of how a hard drive functions. The principle of operation, in general, is quite simple for a basic understanding, but there are some nuances, which will be discussed further.

Questions about the purpose and classification of hard drives?

The question of purpose is, of course, rhetorical. Any user, even the most entry level, will immediately answer that the hard drive (aka hard drive, aka Hard Drive or HDD) will immediately answer that it is used to store information.

In general, this is true. Do not forget that on the hard drive, in addition to the operating system and user files, there are boot sectors created by the OS, thanks to which it starts, as well as certain labels by which you can quickly find them on the disk necessary information.

Modern models are quite diverse: regular HDDs, external hard drives, high-speed solid-state SSD drives, although it is not customary to classify them specifically as hard drives. Next, we propose to consider the device and principle work hard disk, if not in full, then at least enough to understand the basic terms and processes.

Please note that there is also a special classification of modern HDDs according to some basic criteria, among which are the following:

• method of storing information;
• media type;
• way of organizing access to information.

Why is a hard drive called a hard drive?

Today, many users are wondering why they call hard drives related to small arms. It would seem, what could be common between these two devices?

The term itself appeared back in 1973, when the world's first HDD appeared on the market, the design of which consisted of two separate compartments in one sealed container. The capacity of each compartment was 30 MB, which is why the engineers gave the disk the code name “30-30”, which was fully in tune with the brand of the “30-30 Winchester” gun, popular at that time. True, in the early 90s in America and Europe this name almost fell out of use, but it still remains popular in the post-Soviet space.

The structure and principle of operation of a hard drive

But we digress. The principle of operation of a hard drive can be briefly described as the processes of reading or writing information. But how does this happen? In order to understand the principle of operation of a magnetic hard drive, you first need to study how it works.

The hard drive itself is a set of plates, the number of which can range from four to nine, connected to each other by a shaft (axis) called a spindle. The plates are located one above the other. Most often, the materials for their manufacture are aluminum, brass, ceramics, glass, etc. The plates themselves have a special magnetic coating in the form of a material called platter, based on gamma ferrite oxide, chromium oxide, barium ferrite, etc. Each such plate is about 2 mm thick.

Radial heads (one for each plate) are responsible for writing and reading information, and both surfaces are used in the plates. For which it can range from 3600 to 7200 rpm, and two electric motors are responsible for moving the heads.

In this case, the basic principle of operation of a computer hard drive is that information is not recorded just anywhere, but in strictly defined locations, called sectors, which are located on concentric paths or tracks. To avoid confusion, uniform rules apply. This means that the principles of operation of hard drives, from the point of view of their logical structure, are universal. For example, the size of one sector, adopted as a uniform standard throughout the world, is 512 bytes. In turn, sectors are divided into clusters, which are sequences of adjacent sectors. And the peculiarities of the operating principle of a hard drive in this regard are that the exchange of information is carried out by entire clusters (an entire number of chains of sectors).

But how does information reading happen? The principles of operation of a hard magnetic disk drive are as follows: using a special bracket, the reading head is moved in a radial (spiral) direction to the desired track and, when rotated, is positioned above a given sector, and all heads can move simultaneously, reading the same information not only from different tracks , but also from different disks (plates). All tracks with the same serial numbers are usually called cylinders.

In this case, one more principle of hard drive operation can be identified: the closer the reading head is to the magnetic surface (but does not touch it), the higher the recording density.

How is information written and read?

Hard drives, or hard drives, were called magnetic because they use the laws of the physics of magnetism, formulated by Faraday and Maxwell.

As already mentioned, plates made of non-magnetic sensitive material are coated with a magnetic coating, the thickness of which is only a few micrometers. During operation, a magnetic field appears, which has a so-called domain structure.

A magnetic domain is a magnetized region of a ferroalloy strictly limited by boundaries. Further, the principle of operation of a hard drive can be briefly described as follows: when an external influence occurs magnetic field, the disk’s own field begins to be oriented strictly along the magnetic lines, and when the influence stops, zones of residual magnetization appear on the disks, in which the information that was previously contained in the main field is stored.

The reading head is responsible for creating an external field when writing, and when reading, the zone of residual magnetization, being opposite the head, creates electromotive force or EMF. Then everything is simple: the change in EMF corresponds to unity in binary code, and its absence or termination is zero. The time of change of the EMF is usually called a bit element.

In addition, the magnetic surface, purely from computer science considerations, can be associated as a certain point sequence of information bits. But, since the location of such points cannot be calculated absolutely accurately, you need to install some pre-designed markers on the disk that help determine the desired location. Creating such marks is called formatting (roughly speaking, dividing the disk into tracks and sectors combined into clusters).

Logical structure and principle of operation of a hard drive in terms of formatting

As for the logical organization of the HDD, formatting comes first here, in which two main types are distinguished: low-level (physical) and high-level (logical). Without these steps, there is no talk of bringing the hard drive into working condition. How to initialize a new hard drive will be discussed separately.

Low-level formatting involves physical impact onto the surface of the HDD, which creates sectors located along the tracks. It is curious that the principle of operation of a hard drive is such that each created sector has its own unique address, which includes the number of the sector itself, the number of the track on which it is located, and the number of the side of the platter. Thus, when organizing direct access the same RAM accesses directly to a given address, rather than searching for the necessary information across the entire surface, due to which performance is achieved (although this is not the most important thing). Please note that when executing low level formatting Absolutely all information is erased, and in most cases it cannot be restored.

Another thing is logical formatting (in Windows systems this is quick formatting or Quick format). In addition, these processes are also applicable to the creation of logical partitions, which are a certain area of ​​the main hard drive that operate on the same principles.

Logical formatting primarily affects the system area, which consists of the boot sector and partition tables (Boot record), file allocation tables (FAT, NTFS, etc.) and root directory(Root Directory).

Information is written to sectors through the cluster in several parts, and one cluster cannot contain two identical objects (files). Actually, creating a logical partition, as it were, separates it from the main one system partition, as a result of which the information stored on it is not subject to change or deletion in the event of errors and failures.

Main characteristics of HDD

It seems that in general terms the principle of operation of a hard drive is a little clear. Now let's move on to the main characteristics, which give a complete picture of all the capabilities (or shortcomings) of modern hard drives.

The operating principle of a hard drive and its main characteristics can be completely different. To understand what we are talking about, let’s highlight the most basic parameters that characterize all information storage devices known today:

• capacity (volume);
• performance (data access speed, reading and writing information);
• interface (connection method, controller type).

Capacity represents the total amount of information that can be written and stored on a hard drive. The HDD production industry is developing so quickly that today hard drives with capacities of about 2 TB and higher have come into use. And, as it is believed, this is not the limit.

The interface is the most significant characteristic. It determines exactly how the device connects to motherboard, which controller is used, how reading and writing is done, etc. The main and most common interfaces are IDE, SATA and SCSI.

Disks with an IDE interface are inexpensive, but the main disadvantages include: limited quantity simultaneously connected devices (maximum four) and low data transfer speed (even with support for direct memory access Ultra DMA or Ultra ATA protocols (Mode 2 and Mode 4). Although, it is believed that their use can increase the read/write speed up to level of 16 Mb/s, but in reality the speed is much lower.In addition, to use the UDMA mode, you need to install a special driver, which, in theory, should be included with motherboard.

When talking about the principle of operation of a hard drive and its characteristics, we cannot ignore which is the successor to the IDE ATA version. The advantage of this technology is that the read/write speed can be increased to 100 MB/s through the use of the high-speed Fireware IEEE-1394 bus.

Finally, the SCSI interface, compared to the previous two, is the most flexible and fastest (write/read speeds reach 160 MB/s and higher). But such hard drives cost almost twice as much. But the number of simultaneously connected information storage devices ranges from seven to fifteen, the connection can be made without turning off the computer, and the cable length can be about 15-30 meters. Actually, this one HDD type For the most part, it is used not on user PCs, but on servers.

Speed, which characterizes the transmission speed and throughput I/O, usually expressed in terms of transfer time and the amount of sequential data transferred and expressed in MB/s.

Some additional options

Speaking about what the operating principle of a hard drive is and what parameters affect its functioning, we cannot ignore some additional characteristics that may affect the performance or even the lifespan of the device.

Here, the first place is the rotation speed, which directly affects the time of search and initialization (recognition) of the desired sector. This is the so-called latent search time - the interval during which the required sector rotates towards the read head. Today, several standards have been adopted for spindle speed, expressed in revolutions per minute with a delay time in milliseconds:

• 3600 - 8,33;
• 4500 - 6,67;
• 5400 - 5,56;
• 7200 - 4,17.

It is easy to see that the higher the speed, the less time is spent searching for sectors, and in physical terms, per revolution of the disk before setting the head to the desired platter positioning point.

Another parameter is the internal transmission speed. On external tracks it is minimal, but increases with a gradual transition to internal tracks. Thus, the same defragmentation process, which is moving frequently used data to the fastest areas of the disk, is nothing more than moving it to the internal track with higher speed reading. External speed has fixed values ​​and directly depends on the interface used.

Finally, one of important points is associated with the presence of the hard drive's own cache memory or buffer. In fact, the principle of operation of a hard drive in terms of buffer use is somewhat similar to RAM or virtual memory. The larger the cache memory (128-256 KB), the faster the hard drive will work.

Main requirements for HDD

There are not so many basic requirements that are imposed on hard drives in most cases. Main - long term service and reliability.

The main standard for most HDDs is a service life of about 5-7 years with an operating time of at least five hundred thousand hours, but for high-end hard drives this figure is at least a million hours.

As for reliability, the S.M.A.R.T. self-testing function is responsible for this, which monitors the condition of individual elements of the hard drive, carrying out constant monitoring. Based on the collected data, even a certain forecast of the appearance of possible malfunctions further.

It goes without saying that the user should not remain on the sidelines. So, for example, when working with a HDD, it is extremely important to maintain the optimal temperature regime (0 - 50 ± 10 degrees Celsius), avoid shakes, impacts and falls of the hard drive, dust or other small particles getting into it, etc. By the way, many will It is interesting to know that the same particles of tobacco smoke are approximately doubled more distance between the reading head and the magnetic surface of the hard drive, and a human hair - 5-10 times.

Initialization issues in the system when replacing a hard drive

Now a few words about what actions need to be taken if for some reason the user changed the hard drive or installed an additional one.

We will not fully describe this process, but will focus only on the main stages. First you need to connect the hard drive and look at it BIOS settings, whether new equipment has been identified, in the disk administration section, initialize and create boot entry, create a simple volume, assign it an identifier (letter) and format it with a choice of file system. Only after this the new “screw” will be completely ready for work.

Conclusion

That, in fact, is all that briefly concerns the basic functioning and characteristics of modern hard drives. The principle of operation of an external hard drive was not fundamentally considered here, since it is practically no different from what is used for stationary HDDs. The only difference is the method of connecting the additional drive to a computer or laptop. The most common connection is via a USB interface, which is directly connected to the motherboard. At the same time, if you want to ensure maximum performance, it is better to use USB standard 3.0 (the port inside is painted blue), of course, provided that the external HDD itself supports it.

Otherwise, I think that many people have at least a little understood how a hard drive of any type functions. Perhaps too many topics were given above, especially even from a school physics course, however, without this, it will not be possible to fully understand all the basic principles and methods inherent in the technologies for producing and using HDDs.

We, the users personal computer, we often come across the abbreviation HDD. And the desire to know what a HDD is, where it is and what it is needed for is justified.

HDD stands for " hard disk drive". Simply put, it is a hard drive. They are gradually becoming a thing of the past, being replaced by SSDs, but HDDs will occupy their niche in the market for a long time.

Why is the drive "hard"

There is no name for HDD in a computer. Hard drive, hard drive, hard drive, screw - just a small list of its names. Why "hard disk drive"?

Unlike “floppy” disks (floppy disks), data on HDDs is recorded on hard plates, and they, in turn, are covered with a layer of ferromagnetic material. They are called nothing more than “magnetic disks”. A hard drive uses one or more platters on one axis. Reading devices (heads) do not touch the surface of the plates during operation. This is explained simply: with the rapid rotation of the plates, a layer of incoming air flow is formed. The distance between the reading device and the working surface is very small - only a few nanometers, and the air layer, which eliminates mechanical contact, ensures a long service life. If the plates do not rotate at the proper speed, then the heads are in the so-called “parking” zone - outside the boundaries of the plates.

A distinctive property of a HDD in a computer is that the storage medium is combined with a drive, as well as with a block of necessary electronics in one housing.

Main characteristics of HDD

Like any technical device, the hard drive has a number of characteristics, based on which we can draw conclusions about its relevance.

• Capacity is one of the most significant quantities. Characterizes the amount of data that can be stored by the drive.
• Dimensions (form factor). The most common variations are 3.5 and 2.5 inches. Defines the width of the device.
• Rotation speed of the axis and spindle. The number of its revolutions per minute. The parameter significantly affects the speed of data access and directly the speed of their transfer. The most common options: 4200, 5400, 7200, 10,000 rpm.
• The number of I/O operations per second. For modern disks this number approaches 50 (with random access to data); with sequential access, it is correspondingly higher - about 100.
• Energy consumption is an important parameter for portable devices(we're talking about laptops/netbooks).
• Buffer size. Buffer is intermediate memory. Its purpose is to smooth out differences in read/write speeds. In modern HDDs it is usually located in the range from 8 to 64 megabytes.

I hope we were able to understand what a HDD is in a computer, and even expand our horizons a little in the world of computer hardware.