What is a computer hard drive? FAQ Battle of HDD and SSD. What's the difference and which one to choose? Hard drive what does it do

What is HDD, hard disk and hard drive - these words are different widely used terms for the same device that is part of the computer. In connection with the need to store information on a computer, devices appeared, information keepers like a hard disk and became an integral part of a personal computer.

Earlier, on the first computers, information was stored on punched tapes - this is cardboard paper with punched holes; the next step in the development of a computer was a magnetic recording, the principle of which is preserved in today's hard drives. Unlike today's terabyte HDDs, the information to be stored on them totaled tens of kilobytes, which is insignificant in comparison with today's information.

What is HDD and its functionality for?

HDD is a read-only memory device of a computer, that is, its main function is long-term data storage. HDD, unlike RAM, is not considered volatile memory, that is, after disconnecting power from the computer, and then, as a result, from the hard disk, all information previously saved on this drive will be saved. It turns out that the hard disk serves as the best place on the computer for storing personal information: files, photos, documents and videos will obviously be stored on it for a long time, and the saved information can be used in the future for your own needs.

ATA / PATA (IDE) - this parallel interface is used not only for connecting hard drives, but also for reading discs - optical drives. Ultra ATA is the most advanced representative of the standard and has a possible data rate of information up to 133 megabytes per second. The specified method of data transfer is considered very outdated and today is used in outdated computers; on modern motherboards, you will not be able to find an IDE connector.

SATA (Serial ATA) - is a serial interface, which has become a good replacement for the outdated PATA and, unlike it, there is an opportunity to connect only one device, but on budget motherboards there are several connectors for connection. The standard is subdivided into revisions with different data transfer / exchange rates:

• SATA has a data exchange rate of up to 150 Mb / s. (1.2 Gbps);
• SATA rev. 2.0 - for this revision, the data exchange speed in comparison with the first SATA interface has doubled to 300 MB / s (2.4 Gb / s);
• SATA rev. 3.0 - data exchange for the revision has become even higher up to 6 Gb / s (600 MB / s).

All of the above-described connection interfaces of the SATA family are interchangeable, but by connecting, for example, a hard drive with a SATA 2 interface to the SATA motherboard connector, the data exchange with the hard drive will take place based on the oldest revision, in this case SATA revision 1.0.

Hard disk or HDD it is a device that allows you to store information for a long time and which is non-volatile. In simple words, an iron box where all your documents, movies, operating system and everything else are kept. If we draw a life analogy, then this is something like a big album. With a pencil in hand, you can draw or write essays. If you don't like something, then you can always take the "eraser". The bottom line is that while the album is in the shelf, all the data remains intact.

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

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

Let's consider this box in more detail.

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

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

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

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

It is also worth knowing that there may be several such plates inside the hard drive box. As you probably already guessed, the number of pancakes affects the amount of information stored. But, it is not limited to this. For example, a long time ago the disks were 1.5 times larger than today's ones, and they could fit 20-40MB.

Figure 1. Simplified diagram of a circular hard drive

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

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

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

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

Note: I also advise you to read the article Solid state hard drive or SSD drive, as this is the next round of storage devices.

Hard drive specifications

If, I hope, it became clear to you with the device of hard drives, then for the sake of completeness, it remains to consider the issue of the main characteristics of the HDD.

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

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

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

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

5. Impact resistance or in common people vitality... Basically, it denotes what kind of overload the hard drive can take without damaging the data. Nevertheless, I strongly advise against checking this characteristic.

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

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

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

Features of the design of hard drives

A modern hard drive consists of several metal disks on which information is recorded. The discs are covered with iron oxide or another special compound capable of storing the effect of a magnetic field. The number of discs depends on the volume of the medium and usually ranges from 1 to 3. Metal discs are perfectly flat, smooth and balanced, so they can rotate at high speed, according to the standard it can be 5400, 7200 or 10000 rpm.

Special heads move along the discs with the highest positioning accuracy. Each disk has 2 magnetic heads. Reading data from the surface of the disks is carried out using the installation of special magnetoresistive heads, they work depending on how the magnetic field changes on the surface of the disk. The data is transmitted to the computer as a result of receiving an analog signal that is converted into digital form.

On discs, information is found in tracks along a circle. To work with the data on the media, the magnetic heads move along the tracks. The movement of the heads is carried out using a special solenoid drive. These heads can access any place on the disc due to their high rotation speed. The heads are located on both sides of the discs, so each of them does the work on one side and is fully responsible for it.

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

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

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

Hard drives are designed for use in home PCs, and there are also for use in servers. The latter are much more demanding, because they work with a significant load and must provide high productivity and speed of work.

Characteristics of hard drives

In order to choose the right hard drive for certain purposes, you need to understand a large number of characteristics. The first thing to look out for is the form factor. On stationary PCs, 3.5-inch hard drives are installed, and on laptops - 2.5. There are other less common form factors as well. The second important parameter is the interface through which the device is connected to the computer. Various variations of the SATA interface are used on the PC.

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

When choosing a hard disk, you should pay attention to the buffer size, which directly affects the speed of the device with information.

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

If the device is planned to be frequently transferred from one computer to another, then such parameter as shock resistance is important. The higher it is, the less likely it is to lose information on impact or damage the hard drive.

While working with information, the disk gives the requested information at a certain speed. This indicator is called "Random access time" and the less it is, the faster the request will be transmitted.

Having an idea of \u200b\u200ball the parameters, characteristics and structure of modern hard drives, you can quickly find the right hard drive for performing the tasks on your PC.

When the computer starts up, a set of firmware written in the BIOS chip checks the hardware. If everything is in order, it transfers control to the operating system loader. Then the OS is loaded and you start using the computer. In this case, where was the operating system stored before turning on the computer? How did your essay, which you wrote all night, remain intact after turning off the power of the PC? Again, where is it stored?

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

Traditionally, let's take a look at the definition of a hard drive on Wikipedia:

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

They are used in the vast majority of computers, as well as separately connected devices for storing backup copies of data, as file storage, etc.

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

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

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

It is important that the HDD memory is not volatile, that is, it does not matter whether the power is connected or not, the information recorded on the device will not disappear anywhere. This is an important difference between permanent computer memory and temporary ().

Looking at a computer's hard drive in real life, you will not see any 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

Consider what is HDD 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 hard drive:

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

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

What does a hard drive consist of?

We partially mentioned about the composite hard disk, now we will deal with this in more detail. So, the main components of the HDD:

• Housing - protects the hard drive mechanisms from dust and moisture. As a rule, it is sealed so that the very moisture and dust do not get inside;
• Discs (pancakes) - plates from a certain alloy of metals, coated on both sides, on which data is recorded. The number of plates can be different - from one (in budget versions) to several;
• Engine - on the spindle of which pancakes are fixed;
• Head block - construction of interconnected levers (rocker arms) and heads. Part of the hard disk 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 at the end of the head block;
• Controller - an electronic microcircuit that controls the operation of the HDD;
• Parking area - a place inside the hard drive next to the disks or on their inner part, where the heads are lowered (parked) during idle time, so as not to damage the working surface of the pancakes.

Such is the simple device of the hard 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 a hard drive works

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

This sequence (first, the discs spin, and then the heads start to work) is necessary so that due to the formed air flow, the heads float above the plates. Yes, they never touch the surface of the discs, otherwise the discs 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 starting, first of all, it reads service information about the state of the hard disk and other necessary information about it, located on the so-called zero track. Only then does the work with data begin.

Information on the computer's hard disk is recorded on tracks, which, in turn, are divided into sectors (a kind of 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" partitioning of the disk, there is also a conditional "vertical". Since all heads are combined, they are always positioned above the same track number, each above its own disc. Thus, during the operation of the HDD, 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. Then the result is checked. In addition to writing data directly to the disk, information also goes to its cache.

If the controller receives a command to read, the first thing to check is the presence of the required information 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 supply to the hard drive disappears, the heads are automatically parked in the parking zone.

This is, in general terms, how a computer's hard drive works. In reality, everything is much more complicated, but an ordinary user, most likely, does not need such details, so we will finish with this section and move on.

Types of hard drives and their manufacturers

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

If we talk about the types of HDDs, 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 located in the laptop case;
2. For a PC - in this case, it is also possible to use 2.5 ″ hard drives, but as a rule, 3.5 inches are used;
3. External hard drives are devices that are separately connected to a PC / laptop, most often acting as a file storage.

There is also a special type of hard drives for servers. They are identical to conventional PCs, but may differ in connection interfaces and higher performance.

All other divisions of HDD into types come from their characteristics, so we will consider them.

Hard drive specifications

So, the main characteristics of a computer hard drive:

• Volume - an indicator of the maximum possible amount of data that can be stored on a disk. The first thing to look at when choosing an HDD. This figure can reach 10 TB, although 500 GB - 1 TB is more often chosen for a home PC;
• Form factor Is the 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 on the PC and on the server. The form factor also affects the volume, since a larger disk can fit more data;
• Spindle speed - how fast 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 higher both values;
• Interface - method (connector type) of connecting the HDD to the computer. The most popular interface for internal hard drives today is SATA (older computers used IDE). External hard drives are usually connected via USB or FireWire. In addition to those listed, there are also such interfaces as SCSI, SAS;
• Buffer volume (cache memory) - a type of fast memory (by the type of RAM) installed on the hard disk controller, intended 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. Fluctuates from 3 to 15 ms;

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

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

What is HDD for?

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

HDD is computer memory. Do not confuse it with RAM. Hard disk - volatile memory, RAM - volatile.

Winchester is now the main storage device, and if you have a computer, then there is a screw.

How HDD works

Hard disks, that is, HDDs, work similarly to a device that everyone has long forgotten about - a "turntable", with a rotating disc and a needle for playing music. Converting elements (read / write heads) used in hard drives are similar to read / write heads that are used in video and stereo cassette recorders to access information on magnetic media.

In hard drives, information is stored on a rotating metal or glass plate covered with a magnetic material. As a rule, a disc consists of several plates connected by a common rod - a spindle. Each record is something like a vinyl record with a record played back by a turntable. Information is usually stored on both sides of the plate.

As the disc spins, an element called a head reads or writes binary data onto the magnetic medium. The information on the disc is recorded using any coding method, of which there are a great many. The encoding method and recording density are determined by the disc controller.

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

Past and future of HDD

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

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

By the way, now Seagate hard drives are the best-selling in Europe. And in Russia, who does not know the famous Barracuda?

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

Need to know

1. HDD is a complex piece of information storage

2. The hard disk is short-lived and with constant use it is unlikely to live more than three years

3. It is highly undesirable to carry a hard disk (somewhere), twirl it in your hands and generally take it out of the computer case. Winchester is very sensitive to vibration!

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

5. Fans of poking around in hardware need to remember that by opening the HDA, you are putting an end to both the information and the hard drive itself

6. In terms of storage safety, information carriers can be arranged in the following order (with increasing risk of data loss): head, paper, hard drive. Do not store important information on HDD! And if you have to - constantly make a backup!

7. If the information on the hard disk is not available for some reason, do not try to recover it! Most likely, you will only finally destroy it - it is better to contact the professionals. Recovering information is not a dumb thing for you!

8. The word "HDD" is abusive and is not used in a decent society, it characterizes something (to put it mildly) unreliable, short-lived and disgusting