What is HDD? Hard drive, what is it? What does a hard drive consist of and how does it work? Pros and cons of HDD compared to SSD What does hdd mean?

What is HDD, hard drive and hard drive - these words are different widely used terms for the same device that is part of the computer. Due to the need to store information on a computer, information storage devices such as a hard drive appeared and became an integral part of a personal computer.

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

Why do you need a HDD and its functionality?

HDD is a computer's permanent storage device, that is, its main function is long-term data storage. HDD, unlike RAM, is not considered volatile memory, that is, after turning off the power from the computer, and then, as a result, from the hard drive, all information previously stored on this drive will certainly be preserved. It turns out that the hard drive serves as the best place on the computer for storing personal information: files, photographs, documents and videos will obviously be stored on it for a long time, and the stored information can be used in the future for your needs.

ATA/PATA (IDE)- this parallel interface serves not only to connect hard drives, but also disk reading devices - optical drives. Ultra ATA is the most advanced representative of the standard and has a possible data usage speed of up to 133 megabytes per second. This method of data transfer is considered very outdated and today is used in outdated computers; IDE connectors can no longer be found on modern motherboards.

SATA (Serial ATA)- is a serial interface, which has become a good replacement for the outdated PATA and, unlike it, it is possible to connect only one device, but on budget motherboards there are several connectors for connection.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

• SATA has a data transfer speed of up to 150 Mb/s. (1.2 Gbit/s);
• SATA rev. 2.0 - in this revision, the data exchange speed in comparison with the first SATA interface has increased 2 times to 300 MB/s (2.4 Gbit/s);
• SATA rev. 3.0 - data exchange for the revision has become even higher up to 6 Gbit/s (600 MB/s).

All of the above-described connection interfaces of the SATA family are interchangeable, but if you connect, for example, a hard drive with a SATA 2 interface to a SATA motherboard connector, data exchange with the hard drive will be based on the highest revision, in this case SATA revision 1.0.

Until recently, when purchasing a new computer and choosing the drive to install, the user had only one choice - HDD HDD. And then we were interested in only two parameters: spindle speed (5400 or 7200 RPM), disk capacity and cache size.

Let's look at the pros and cons of both types of drives and make a clear comparison of HDD and SSD.

Principle of operation

A traditional drive, or ROM (read only memory) as it is commonly called, is needed to store data even after a complete power outage. Unlike RAM (random access memory) or RAM, data stored in memory is not erased when the computer is turned off.

A classic hard drive consists of several metal “pancakes” with a magnetic coating, and data is read and written using a special head that moves above the surface of the disk rotating at high speed.

Solid state drives have a completely different operating principle. The SSD completely lacks any movable components, and its “internals” look like a set of flash memory chips located on one board.

Such chips can be installed either on the system’s motherboard (for particularly compact models of laptops and ultrabooks), on a PCI Express card for desktop computers, or on a special laptop slot. The chips used in SSDs are different from those we see in a flash drive. They are much more reliable, faster and more durable.

Disc history

Hard magnetic disks have a very long history (of course, by the standards of computer technology development). In 1956, IBM released a little-known computer IBM 350 RAMAC, which was equipped with a huge storage device of 3.75 MB by those standards.

These cabinets could store as much as 7.5 MB of data

To build such hard drive I had to install 50 round metal plates. The diameter of each was 61 centimeters. And this entire gigantic structure could store... just one MP3 song with a low bitrate of 128 Kb/s.

Until 1969, this computer was used by the government and research institutes. Just some 50 years ago, a hard drive of this size was quite suitable for humanity. But standards changed dramatically in the early 80s.

5.25-inch (13.3 centimeter) floppy disks appeared on the market, and a little later 3.5- and 2.5-inch (laptop) versions. Such floppy disks could store up to 1.44 MB of data, and a number of computers of that time were supplied without a built-in hard drive. Those. To start the operating system or software shell, you had to insert a floppy disk, then enter several commands and only then start working.

Over the entire history of hard drive development, several protocols have been changed: IDE (ATA, PATA), SCSI, which later transformed into the now famous SATA, but all of them performed the only function of a “connecting bridge” between motherboard and a hard drive.

From 2.5 and 3.5-inch floppy disks with a capacity of one and a half thousand kilobytes, the computer industry has moved to hard drives of the same size, but with thousands of times more memory. Today, the capacity of top 3.5-inch HDD drives reaches 10 TB (10,240 GB); 2.5-inch - up to 4 TB.

The history of solid-state SSDs is much shorter. Engineers started thinking about releasing a memory storage device that would be devoid of moving elements back in the early 80s. The appearance in this era of the so-called bubble memory was met with very hostility and the idea proposed by the French physicist Pierre Weiss back in 1907 did not take root in the computer industry.

The essence of bubble memory was to split magnetized permalloy into macroscopic regions that would have spontaneous magnetization. The unit of measurement for such a storage device was bubbles. But the most important thing is that such a drive had no hardware moving elements.

They quickly forgot about bubble memory, and only remembered it during the development of a new class of drives - SSDs.

SSDs appeared in laptops only in the late 2000s. In 2007, the budget laptop OLPC XO-1, equipped with 256 MB of RAM, entered the market. AMD processor Geode LX–700 with a frequency of 433 MHz and the main highlight is 1 GB NAND flash memory.

The OLPC XO-1 was the first laptop to use a solid-state drive. And soon it was joined by the legendary line of netbooks from Asus EEE PC with model 700, where the manufacturer installed a 2 GB SSD drive.

In both laptops, the memory was installed directly on the motherboard. But soon manufacturers revised the principle of organizing drives and approved a 2.5-inch format connected via the SATA protocol.

The capacity of modern SSD drives can reach 16 TB. More recently, Samsung introduced just such an SSD, albeit in a server version and with a price that is astronomical for the average person.

Pros and cons of SSD and HDD

The tasks of each class of drives boil down to one thing: to provide the user with a working operating system and allow him to store personal data. But both SSD and HDD have their own characteristics.

Price

SSDs are much more expensive than traditional HDDs. To determine the difference, a simple formula is used: the price of the drive is divided by its capacity. As a result, the cost of 1 GB of capacity in foreign currency is obtained.

So, a standard 1 TB HDD costs an average of $50 (3,300 rubles). The cost of one gigabyte is $50/1024 GB = $0.05, i.e. 5 cents (3.2 rubles). In the world of SSDs, everything is much more expensive. An SSD with a capacity of 1 TB will cost an average of $220, and the price for 1 GB according to our simple formula will be 22 cents (14.5 rubles), which is 4.4 times more expensive than an HDD.

The good news is that the cost of SSDs is rapidly decreasing: manufacturers are finding cheaper solutions for the production of drives and the price gap between HDDs and SSDs is narrowing.

Average and maximum capacity of SSD and HDD

Just a few years ago, there was not only a numerical, but also a technological gap between the maximum capacity of HDD and SSD. It was impossible to find an SSD that could compete with an HDD in terms of the amount of stored information, but today the market is ready to provide the user with such a solution. True, for impressive money.

The maximum capacity of SSDs offered for the consumer market is 4 TB. A similar option in early July 2016. And for 4 TB of space you will have to pay $1,499.

The basic amount of HDD memory for laptops and computers produced in the second half of 2016 ranges from 500 GB to 1 TB. Models similar in power and characteristics, but with an installed SSD drive, are content with only 128 GB.

SSD and HDD speed

Yes, it is for this indicator that the user overpays when he prefers SSD storage. Its speed is many times higher than that of an HDD. The system can boot in just a few seconds, launching heavy applications and games takes significantly less time, and copying large amounts of data turns from a multi-hour process into a 5-10 minute process.

The only “but” is that data from the SSD drive is deleted as quickly as it is copied. Therefore, when working with an SSD, you may simply not have time to press the cancel button if one day you suddenly delete important files.

Fragmentation

The favorite “delicacy” of any HDD hard drive is large files: movies in MKV format, large archives and BlueRay disk images. But as soon as you load the hard drive with a hundred or two small files, photographs or MP3 songs, the reading head and metal pancakes become confused, as a result of which the recording speed drops significantly.

After the HDD fills up and files are repeatedly deleted/copied, the hard drive starts to work slower. This is due to the fact that parts of the file are scattered across the entire surface of the magnetic disk and when you double-click on a file, the reading head is forced to look for these fragments from different sectors. This is how time is wasted. This phenomenon is called fragmentation, and as preventive measures to speed up the HDD, a software and hardware process is provided defragmentation or arranging such blocks/parts of files into a single chain.

The operating principle of an SSD is fundamentally different from a HDD, and any data can be written to any memory sector with further instant reading. This is why defragmentation is not needed for SSD drives.

Reliability and service life

Remember the main advantage of SSD drives? That's right, no moving parts. This is why you can use a laptop with an SSD in transport, off-road or in conditions inevitably associated with external vibrations. This will not affect the stability of the system and the drive itself. The data stored on the SSD will not be damaged even if the laptop falls.

With HDD everything is exactly the opposite. The read head is located just a few micrometers from the magnetized blanks, and therefore any vibration can lead to the appearance of “ bad sectors» - areas that become unusable for work. Regular shocks and careless handling of a computer that runs on an HDD will lead to the fact that sooner or later such a hard drive will simply, in computer jargon, “crumble” or stop working.

Despite all benefits of SSD, they also have a very significant drawback - a limited use cycle. It directly depends on the number of rewrite cycles of memory blocks. In other words, if you copy/delete/re-copy gigabytes of information every day, you will very soon cause the clinical death of your SSD.

Modern SSD drives are equipped with a special controller that ensures that data is evenly distributed across all SSD blocks. Thus, it was possible to significantly increase the maximum operating time to 3000 – 5000 cycles.

How durable is an SSD? Just take a look at this picture:

And then compare it with the warranty period promised by the manufacturer of your specific SSD. 8 – 13 years for storage, believe me, is not so bad. And we shouldn’t forget about the progress that leads to a constant increase in the capacity of SSDs at a constantly decreasing cost. I think in a few years your 128 GB SSD will be considered a museum piece.

Form factor

The battle between drive sizes has always been driven by the type of devices in which they are installed. So, for a desktop computer, installing both a 3.5-inch and a 2.5-inch drive is absolutely uncritical, but for portable devices such as laptops, players and tablets, a more compact option is needed.

The 1.8-inch format was considered the smallest serial version of the HDD. This is the same disc that was used in the now discontinued iPod Classic player.

And no matter how hard the engineers tried, they failed to build a miniature HDD hard drive with a capacity of more than 320 GB. It is impossible to break the laws of physics.

In the world of SSDs, everything is much more promising. The generally accepted 2.5-inch format became such not because of any physical limitations faced by technology, but only due to compatibility. In the new generation of ultrabooks, the 2.5' format is gradually being abandoned, making drives more and more compact, and the bodies of the devices themselves thinner.

Noise

The rotation of disks, even in the most advanced HDD hard drive, is inseparably associated with the occurrence of noise. Reading and writing data sets the disk head in motion, which moves at an insane speed across the entire surface of the device, which also causes a characteristic crackling sound.

SSD drives are absolutely silent, and all processes occurring inside the chips take place without any accompanying sound.

Bottom line

To summarize the comparison between HDD and SSD, I would like to clearly define the main advantages of each type of drive.

Advantages of HDD: capacious, inexpensive, accessible.

Disadvantages of HDD: slow, afraid of mechanical influences, noisy.

Advantages of SSD: absolutely silent, wear-resistant, very fast, no fragmentation.

Disadvantages of SSD: expensive, theoretically have a limited service life.

Without exaggeration, we can say that one of the most effective methods The only way to upgrade an old laptop or computer is to install an SSD drive instead of an HDD. Even with the latest version of SATA, you can achieve a threefold increase in performance.

Answering the question of who needs this or that drive, I will give several arguments in favor of each type.

Hard drives, or hard drives as they are also called, are one of the most important components of a 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 one, will immediately answer that a 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 the necessary information on the disk.

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, it is proposed to consider the structure and principle of operation of a hard drive, if not in full, then at least in such a way that it is 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 drives on 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 disk can be briefly described as follows: when exposed to an external 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, located opposite the head, creates an electromotive force or EMF. Further, everything is simple: a change in EMF corresponds to one in binary code, and its absence or termination corresponds to 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 on 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 addresses directly to a given address, rather than searching for the necessary information over the entire surface, due to which performance is achieved (although this is not the most important thing). Please note that when performing 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 table (FAT, NTFS, etc.) and the 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 a limited number of simultaneously connected devices (maximum four) and low data transfer speeds (even if they support Ultra DMA direct memory access or Ultra ATA protocols (Mode 2 and Mode 4).Although they are believed to improve the read/write speed up to 16MB/s, the actual speed is much lower.In addition, to use the UDMA mode, installation is required special driver, which, in theory, should be supplied with the 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 type of HDD is mostly used not in user PCs, but on servers.

Performance, which characterizes the transfer speed and I/O throughput, is 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 disk revolution before installing the head desired point plate positioning.

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 an internal track with a higher read speed. External speed has fixed values ​​and directly depends on the interface used.

Finally, one of the important points is related to 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. The main thing is long service life 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 twice the distance between the read head and the magnetic surface of the hard drive, and 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 a boot record, create a simple volume, assign it an identifier (letter) and format it by selecting a 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 the USB 3.0 standard (the port inside is painted blue), of course, provided that the external HDD supports him.

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.

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

What is HDD for?

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

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

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

Operating principle of HDD

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

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

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

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

The past and future of HDD

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

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

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

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

Need to know

1. HDD is a complex contraption for storing information

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

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

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

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

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

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

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

The hard drive is almost one of the most important elements of a modern computer. Since it is designed primarily for long-term storage of your data, this can be games, movies and other large files stored on your PC. And it would be a shame if it could suddenly break down, as a result of which you could lose all your data, which can be very difficult to recover. And in order to properly operate and replace this element, you need to understand how it works and what a hard drive is.

In this article you will learn about the operation of a hard drive, its components and technical characteristics Oh.

Typically, the main elements of a hard drive are several round aluminum platters. Unlike floppy disks (forgotten floppy disks), they are difficult to bend, hence the name hard disk. In some devices they are installed non-removable and are called fixed (fixeddisk). But in ordinary desktop computers and even some models of laptops and tablets can be replaced without problems.

Figure: Hard drive without top cover

The note!

Why are hard drives sometimes called hard drives and what do they have to do with firearms? Sometime in the 1960s, IBM released what was then a high-speed hard drive with development number 30-30. Which coincided with the designation of the famous Winchester rifled weapon, and therefore this term soon became entrenched in computer slang. But in fact, hard drives have nothing in common with real hard drives.

How does a hard drive work?

Recording and reading of information located on the concentric circles of the hard disk, divided into sectors, is carried out using universal write/read heads.

Each side of the disk has its own track for writing and reading, but the heads are located on a common drive for all disks. For this reason, the heads move synchronously.

YouTube Video: Open Hard Drive Operation

Normal drive operation does not allow contact between the heads and the magnetic surface of the disk. However, if there is no power and the device stops, the heads still fall onto the magnetic surface.

During operation of the hard drive, a small air gap forms between the surface of the rotating platter and the head. If a speck of dust enters this gap or the device is shaken, there is a high chance that the head will collide with the rotating surface. A strong impact can cause the head to fail. This output may result in several bytes being corrupted or the device being completely inoperable. For this reason, in many devices the magnetic surface is alloyed, after which a special lubricant is applied to it to cope with periodic shaking of the heads.

Some modern drives use a loading/unloading mechanism that prevents the heads from touching the magnetic surface even if the power is lost.

High and low level formatting

Using Formatting high level allows the operating system to create structures that make it easier to work with files and data stored on the hard drive. All available partitions (logical drives) are supplied boot sector volume, two copies of the file allocation table, and the root directory. Through the above structures, the operating system manages to distribute disk space, tracking the location of files, as well as bypassing damaged areas on the disk.

In other words, high-level formatting comes down to creating a table of contents for the disk and file system (FAT, NTFS, etc.). “Real” formatting can only be classified as low-level formatting, during which the disk is divided into tracks and sectors. Using the DOS FORMAT command, a floppy disk undergoes both types of formatting at once, while a hard disk undergoes only high-level formatting.

In order to produce low level formatting on your hard drive, you must use special program, most often provided by the disc manufacturer. Formatting floppy disks using FORMAT involves performing both operations, while in the case of hard disks, the above operations should be performed separately. Moreover, the hard drive undergoes a third operation - the creation of partitions, which are a prerequisite for using more than one operating system on one PC.

The organization of several partitions makes it possible to install on each of them its own operating infrastructure with a separate volume and logical drives. Each volume or logical drive has its own letter designation (for example drive C,D or E).

What does a hard drive consist of?

Almost every modern hard drive includes the same set of components:

disks(their number most often reaches 5 pieces);

read/write heads(their number most often reaches 10 pieces);

head drive mechanism(this mechanism sets the heads to the required position);

disk drive motor(a device that causes disks to rotate);

air filter(filters located inside the drive housing);

printed circuit board with control circuits(through this component the drive and controller are managed);

cables and connectors(HDD electronic components).

A sealed box - HDA - is most often used as a housing for disks, heads, head drive mechanism and disk drive motor. Usually this box is a single unit that is almost never opened. Other components not included in the HDA, which include configuration elements, printed circuit board and front panel, are removable.

Automatic head parking and control system

In the event of a power failure, a contact parking system is provided, the task of which is to lower the bar with the heads onto the discs themselves. Regardless of the fact that the drive can withstand tens of thousands of ascents and descents of the read heads, all this must happen in areas specially designated for these actions.

During constant ascents and descents, inevitable abrasion of the magnetic layer occurs. If the drive is shaken after wear and tear, damage to the disk or heads is likely to occur. To prevent the above troubles, modern drives are equipped with a special loading/unloading mechanism, which is a plate that is placed on the outer surface of the hard drives. This measure prevents the head from touching the magnetic surface even if the power is turned off. When the voltage is turned off, the drive automatically “parks” the heads on the surface of the inclined plate.

A little about air filters and air

Almost all hard drives are equipped with two air filters: a barometric filter and a recirculation filter. What distinguishes the above filters from replaceable models used in older generation drives is that they are placed inside the case and are not expected to be replaced until the end of their service life.

Old disks used the technology of constantly moving air in and out of the case, using a filter that needed to be changed periodically.

The developers of modern drives had to abandon this scheme, and therefore the recirculation filter, which is located in the sealed HDA case, is used only to filter the air inside the box from the smallest particles trapped inside the case. Regardless of all precautions taken, small particles still form after repeated landings and takeoffs of the heads. Taking into account the fact that the drive housing is sealed and air is pumped inside it, it continues to function even in a heavily polluted environment.

Interface connectors and connections

Many modern hard drives are equipped with several interface connectors designed to connect to the power source and to the system as a whole. As a rule, the drive contains at least three types of connectors:

interface connectors;

power supply connector;

ground connector.

The interface connectors deserve special attention, since they are designed for the drive to receive/transmit commands and data. Many standards do not exclude the possibility of connecting several drives to one bus.

As mentioned above, HDD drives can be equipped with several interface connectors:

MFM and ESDI- extinct connectors used on the first hard drives;

IDE/ATA- a connector for connecting storage devices, which has long been the most common due to its low cost. Technically, this interface is similar to the 16-bit ISA bus. The subsequent development of IDE standards contributed to an increase in data exchange speed, as well as the emergence of the ability to directly access memory using DMA technology;

Serial ATA- a connector that replaced IDE, which is physically a unidirectional line used for serial data transfer. Being in compatibility mode is similar to the IDE interface, however, the presence of a “native” mode allows you to take advantage of an additional set of capabilities.

SCSI- a universal interface that was actively used on servers for connecting HDDs and other devices. Despite good technical performance, it has not become as widespread as IDE due to its high cost.

SAS- serial analog SCSI.

USB- an interface that is necessary for connecting external hard drives. Information exchange in this case occurs via the USB Mass Storage protocol.

FireWire- a connector similar to USB, required for connecting an external HDD.

Fiber Channel-interface used by high-end systems due to high data transfer rates.

Hard drive quality indicators

Capacity- the amount of information the drive can hold. This figure in modern hard drives can reach up to 4 terabytes (4000 gigabytes);

Performance. This parameter has a direct impact on response time and average information transfer speed;

Reliability– an indicator determined by the mean time between failures.

Physical Capacity Limits

The maximum amount of capacity used by a hard drive depends on a number of factors, including the interface, drivers, operating system and file system.

The first ATA drive, released in 1986, had a capacity limit of 137 GB.

Different BIOS version also contributed to a reduction in the maximum capacity of hard drives, and therefore systems built before 1998 had a capacity of up to 8.4 GB, and systems released before 1994 had a capacity of 528 MB.

Even after solving the problems with the BIOS, the capacity limitation of drives with an ATA connection interface remained; its maximum value was 137 GB. This limitation was overcome through the ATA-6 standard, released in 2001. This standard used an expanded addressing scheme, which, in turn, contributed to an increase in storage capacity to 144 GB. Such a solution made it possible to introduce drives with PATA and SATA interfaces, whose storage capacity is higher than the specified limit of 137 GB.

OS restrictions on maximum volume

Almost all modern operating systems do not impose any restrictions on such an indicator as the capacity of hard drives, which cannot be said about more earlier versions operating systems.

For example, DOS did not recognize hard drives whose capacity exceeded 8.4 GB, since access to the drives in this case was performed through LBA addressing, while in DOS 6.x and earlier versions only CHS addressing was supported.

Limitation hard capacity disk is also available if you install Windows 95. The maximum value of this limit is 32 GB. In addition, updated Windows versions 95 is only supported file system FAT16, which in turn imposes a 2 GB limit on partition sizes. It follows from this that if you use a 30 GB hard drive, it must be divided into 15 partitions.

Windows 98 operating system limitations allow the use of larger hard drives.

Characteristics and parameters

Each hard drive has a list of technical characteristics, according to which its usage hierarchy is established.

The first thing you should pay attention to is the type of interface used. Recently, every computer has begun to use SATA.

Second no less important point- volume free space on your hard drive. Its minimum value today is only 80 GB, while the maximum is 4 TB.

Another important characteristic when purchasing a laptop is the hard drive form factor.

The most popular in this case are models whose size is 2.5 inches, while in desktop PCs the size is 3.5 inches.

You should not neglect the spindle rotation speed, the minimum values ​​are 4200, the maximum is 15000 rpm. All of the above characteristics have a direct impact on the speed of the hard drive, which is expressed in MB/s.

Hard drive speed

Of no small importance are the speed indicators of the hard drive, which are determined by:

Spindle speed, measured in revolutions per minute. Its task does not include directly identifying the real exchange speed; it only allows you to distinguish a faster device from a slower device.

Access time. This parameter calculates the time spent by the hard drive from receiving a command to transmitting information over the interface. Most often I use the average and maximum values.

Head positioning time. This value indicates the time it takes for the heads to move and set up from one track to another track.

Bandwidth or disk performance during sequential transfer of large amounts of data.

Internal data transfer rate or the speed of information transmitted from the controller to the heads.

External baud rate or the speed of information transmitted via the external interface.

A little about S.M.A.R.T.

S.M.A.R.T.– a utility designed to independently check the status of modern hard drives that support PATA and SATA interfaces, as well as operating in personal computers from the operating room Windows system(from NT to Vista).

S.M.A.R.T. calculates and analyzes the state of connected hard drives at equal intervals of time, regardless of whether the operating system or not. After the analysis has been carried out, the diagnostic result icon is displayed in the right corner of the taskbar. Based on the results obtained during S.M.A.R.T. diagnostics, the icon may indicate:

For the excellent condition of every hard drive connected to the computer that supports S.M.A.R.T. technology;

The fact that one or more health indicators do not meet the threshold value, while the Pre-Failure / Advisory parameters have a zero value. The above state of the hard drive is not considered pre-failure, however, if this hard drive contains important information, it is recommended to save it on another medium as often as possible or replace the HDD.

The fact that one or more status indicators do not meet the threshold value, while the Pre-Failure / Advisory parameters have an active value. According to hard drive developers, this is a pre-emergency state, and it is not worth storing information on such a hard drive.

Reliability factor

An indicator such as data storage reliability is one of the most important characteristics of a hard drive. The failure rate of a hard drive is once every hundred years, from which we can conclude that HDD is considered the most reliable source of data storage. At the same time, the reliability of each disk is directly influenced by the operating conditions and the device itself. Sometimes manufacturers supply the market with a completely “raw” product, and therefore neglect backup and you cannot completely rely on the hard drive.

Cost and price

Every day the cost of HDD is becoming less and less. For example, today the price of a 500 GB ATA hard drive averages $120, compared to $1,800 in 1983 for a 10 MB hard drive.

From the above statement we can conclude that the cost of HDDs will continue to fall, and therefore in the future everyone will be able to purchase fairly capacious disks at reasonable prices.