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

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 everyone modern user even in principle understands how it functions HDD. 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 marks 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 drives (SSDs), although they are not generally classified as hard drives. Next, we propose to consider the device and principle of operation hard drive, if not in full, then according to 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? Operating principles of a hard drive magnetic disks look like this: using a special bracket, the reading head moves 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 that 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-designated 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. About how to initialize 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 plate. 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 boot sector and partition tables (boot record 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 is connected to the motherboard, which controller is used, how reading and writing are 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 their use is believed to increase the read/write speed to 16 MB/s, 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 supplied. complete 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, SCSI interface compared to the previous two, it is the most flexible and fastest (write/read speed reaches 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.

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, on which the performance or even the service life of the device may depend.

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 hidden time search - the interval during which the required sector is rotated to 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 usage is somewhat similar to operational 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 occurrence of possible malfunctions in the future can be formed.

It goes without saying that the user should not remain on the sidelines. For example, when working with HDD, it is extremely important to maintain optimal temperature regime(0 - 50 ± 10 degrees Celsius), avoid shocks, impacts and falls of the hard drive, dust or other small particles getting into it, etc. By the way, many will be interested to know that the same particles of tobacco smoke are approximately twice as 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 a boot record, create a simple volume, assign it an identifier (letter) and format with a choice 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. Principle of operation external hard disk was not considered fundamentally 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 (port inside is painted Blue colour), of course, provided that the external HDD itself supports it.

Otherwise, I think many people have at least a little bit of understanding of how a hard drive of any type functions. Perhaps too many topics were given above, especially even from a school physics course, nevertheless, without this, it is possible to fully understand all the basic principles and methods inherent in production technologies and HDD applications, it’s impossible to understand.

How does a hard drive work? What types of hard drives are there? What role do they perform in a computer? How do they interact with other components? You will learn from this article what parameters to consider when choosing and purchasing a hard drive.

HDD- shortened name for " Hard Disk Storage". You will also find English HDD- and slang Winchester or for short Screw.

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

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

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

Three more facts you need to know about hard drives.

The hard drive is the slowest part of the computer. When your computer freezes, pay attention to the hard drive activity indicator. If it blinks frequently or lights up continuously, it means the hard drive is executing commands from one of the programs while all the others are idle, waiting their turn. If the operating system is not fast enough random access memory To run the program, it uses up space on your hard drive, which greatly slows down the entire computer. Therefore, one way to increase the speed of your computer is to increase the size of RAM.
The hard drive is also the most fragile part of a computer. As you learned from the video, the engine spins the disk up to several thousand revolutions per minute. Wherein magnetic heads"float" above the disk in the air flow created by the rotating disk. Distance between disk and heads in modern devices is about 10 nm. If the disk is subjected to shock or vibration at this time, the head may touch the disk and damage the surface containing the data stored on it. As a result, the so-called " badblocks" - unreadable areas due to which the computer cannot read any file or boot the system. When turned off, the heads are “parked” outside work area and overloads from impact are not so scary hard drive. Please make backup copies of important data!
The hard drive capacity is often slightly smaller than what the seller or manufacturer indicates. The reason is that manufacturers indicate disk capacity based on the fact that there are 1,000,000,000 bytes in one gigabyte, while there are 1,073,741,824 of them.

Buying a hard drive

If you decide to increase the storage capacity of your computer by connecting extra hard drive or replacing the old one with a larger one, what do you need to know when purchasing?

First, look under the lid system unit your computer. You need to figure out which interface connecting hard The drive is supported by the motherboard. Today the most common standards are SATA and moribund IDE. They are easy to distinguish by appearance. The picture on the left shows a fragment of a motherboard that is equipped with both types of connectors, but yours will most likely have one of them.

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

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

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

In addition, the main parameters include:

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

Every computer has a hard drive or, as it is often called, a hard drive, which is the main storage location for all information used by the computer and its user. The installed software is stored on the hard drive. 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 media. The amount of information stored on a hard drive depends on its size.

The very first models of hard drives allowed storing up to 10 MB of data on their disks, which was a lot in those days. Nowadays, modern storage devices allow you to store thousands and tens of thousands of megabytes. The memory capacity on modern models is calculated in gigabytes and terabytes. This makes it possible to store great amount movies, music, videos, games and other data. A significant increase in the amount of memory on a 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.

Design features of hard drives

A modern hard drive consists of several metal disks on which information is recorded. The discs are coated with iron oxide or another special compound that can store the effects of a magnetic field. The number of disks depends on the volume of the media and usually ranges from 1 to 3. Metal disks are ideally even, smooth and balanced, due to which they can rotate at high speed; according to the standard, it can be 5400, 7200 or 10000 rpm.

Special heads move along the disks with the highest positioning accuracy. Each disk has 2 magnetic heads. Reading data from the surface of disks is carried out by installing special magnetoresistive heads; they work depending on how the magnetic field on the surface of the disk changes. Data is transferred to a computer as a result of receiving an analog signal that turns into digital form.

On disks, information is located in tracks located around a circle. To work with data stored on media, magnetic heads move along tracks. The heads are moved using a special solenoid drive. Such heads can access any location on the disk thanks to high speed rotation. The heads are located on both sides of the disks, so each of them carries out work on one side and is fully responsible for it.

A sector on a hard drive allows you to store 512 bytes of information, and each track on a hard drive consists of many sectors. Maximum amount The amount of information that can fit on a hard drive depends on the number of sectors, heads and cylinders. In count HDDs may be the same, but their memory volumes will be completely different. This is due to the fact that to increase capacity, 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 external dimensions, and the opportunities, on the contrary, increase.

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

During 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 markings.

There are hard drives designed for use in home PCs, and others for use in servers. The latter are subject to much greater requirements, because they work with a significant load and must provide high productivity and speed.

Characteristics of hard drives

In order to choose the right hard drive suitable for a specific purpose, you need to understand large quantities characteristics. The first thing you should pay attention to is the form factor. On desktop PCs, 3.5-inch hard drives are installed, and on laptops, 2.5-inch ones. There are also other less common form factors. The second important parameter is the interface through which the device is connected to the computer. PCs use various variations of the SATA interface.

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

When choosing a hard drive, you should pay attention to the buffer size, which directly affects the speed of the device’s processing of information.

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

If you plan to frequently move the device from one computer to another, then such a parameter as shock resistance is important. The higher it is, the less likely it is to lose information during an impact or damage the hard drive.

While working with information, the disk provides the requested information at a certain speed. This indicator is called “Random Access Time” and the lower it is, the faster the request will be transmitted.

Having an idea of all the parameters, characteristics and structure of modern hard drives you can quickly select the appropriate hard drive to perform your tasks on your PC.

Until recently, when buying a new computer and choosing the drive to install, the user had only one choice - hard HDD drive. 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 storage device, or ROM (read only memory) as it is commonly called, is needed to store data even after complete shutdown nutrition. 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 PCI card Express for desktop computers or a dedicated 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 a hard drive, 50 round metal plates had to be installed. 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 sole function of a “connecting bridge” between the motherboard and the 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.

IN laptops SSD appeared only in the late 2000s. Entered the market in 2007 budget laptop OLPC XO–1, equipped with 256 MB of RAM, 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 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. Recently Samsung company presented just such an SSD, however, in a server version and with a price that was 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 it is used simple formula: 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 SSD cost is rapidly decreasing: manufacturers are finding cheaper solutions for the production of drives and the price gap between HDD and SSD 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 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.

Principle SSD operation is fundamentally different from HDD, and any data can be written to any memory sector with further instant reading. That's why for SSD drives defragmentation is not needed.

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. Stored on SSD data 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, to use computer jargon, “crumble” or stop working.

Despite all benefits of SSD, they also have quite significant drawback- limited cycle of use. 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 disk is absolutely uncritical, but for portable devices, like laptops, players and tablets, you need a more compact option.

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

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

Summarizing HDD comparisons 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 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.

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

As per tradition, let's take a look definition of hard disk 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 long time store the data recorded on it. The basis of HDD are hard (aluminum) disks with 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.

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

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

Why does a computer need a hard drive?

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

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

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

What does a hard drive consist of?

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

Frame — protects hard drive mechanisms from dust and moisture. As a rule, it is sealed so that moisture and dust do not get inside;
Discs (pancakes) - plates made of a certain metal alloy, coated on both sides, on which data is recorded. The number of plates can be different - from one (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 top and Bottom part he has a working one;
Positioning device (actuator ) - a mechanism that drives the head block. Consists of a pair of permanent neodymium magnets and a coil located at the end of the head block;
Controller — electronic chip work manager HDD;
Parking zone - a place inside the hard drive next to the disks or on their inner part, where the heads are lowered (parked) during downtime, so as not to damage the working surface of the pancakes.

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

How does a hard drive work?

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

This sequence (first the disks spin up, and then the heads start working) is necessary so that, due to the resulting air flow, the heads float above the plates. Yes, they never touch the surface of the disks, otherwise the latter would be instantly damaged. However, the distance from the surface 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.

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

Types of hard drives and their manufacturers

Today, there are actually three main ones on the market manufacturer of rigid 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:

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

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

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

Hard drive specifications

So, the main characteristics of a computer hard drive:

Volume — an indicator of the maximum possible amount of data that can be stored on the disk. The first thing they usually look at when choosing a HDD. This 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) of connecting the HDD to the computer. The most popular interface for internal hard drives today is SATA (older computers used IDE). External hard drives are usually connected via USB or FireWire. In addition to those listed, there are also such interfaces as SCSI, SAS;
Buffer volume (cache memory) - a type of fast memory (like RAM) installed on the hard drive controller, designed for temporary storage of data that is most often accessed. The buffer size can be 16, 32 or 64 MB;
Random access time — the time during which the HDD is guaranteed to write or read from any part of the disk. Ranges from 3 to 15 ms;

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