What are disks in hard drives made of?

For the soul (Hard drive, Hard Disk Drive HDD

) - a random access storage device (information storage device) based on the principle of magnetic recording. It is the main data storage device in most computers. Unlike " Flexible » disk ( Floppy disks ), information in HDD ), information in recorded on hard (aluminum or glass) plates coated with a layer of ferromagnetic material, most often chromium dioxide - magnetic disks. IN

one or more plates are used on one axis. In operating mode, the reading heads do not touch the surface of the plates due to the layer of incoming air flow that forms near the surface during rapid rotation. The distance between the head and the disk is several nanometers, and the absence of mechanical contact ensures a long service life of the device. When the disks do not rotate, the heads are located at the spindle or outside the disk in a safe area, where their abnormal contact with the surface of the disks is excluded.

First hard drive 1957 IN year by company IBM 5 The very first hard drive was developed, and it was developed even before the creation of the personal computer. You would have to pay a tidy sum for it, although it only had the volume MB 10 The very first hard drive was developed, and it was developed even before the creation of the personal computer. You would have to pay a tidy sum for it, although it only had the volume. Then a hard drive with a capacity year by company especially for personal computer PC XT 30 . Winchester had only tracks and more on 30 sectors in every track. " Winchesters " - this is what hard drives began to be called; if abbreviated, then "IN intami ", this came from an analogy with the marking of the company's carbine Winchester – “30/30”

, which was multi-charged. For clarity, let's look at 3.5 inch SATA disk. It will be Seagate.

ST31000333AS 3.5 inch Green PCB with copper tracks, power connectors and called electronics board or control board (P Rinted Circuit Board, PCB ). It is used to control the operation of the hard drive. The black aluminum case and its contents are called a HDA ( Head and Disk Assembly, HDA ), experts also call it “ jar " The body itself without contents is also called.

HDA (base)

Now let's remove the printed circuit board and examine the components placed on it. (The first thing that catches your eye is the large chip located in the middle - the microcontroller, or processor.) Micro Controller Unit, MCU . On modern hard drives, the microcontroller consists of two parts - the(Central Processor Unit, CPU), which performs all calculations, and the channel read/write channel- a special device that converts the analog signal coming from the heads into digital data during a read operation and encodes digital data into an analog signal during writing. The processor has ports input/output (IO ports) to control other components located on the printed circuit board and transmit data via SATA interface.

Memory Chip is a common DDR SDRAM memory. The amount of memory determines the size of the hard drive cache. This PCB contains memory Samsung DDR volume 32 MB, which in theory gives the disk a cache in 32 MB(and this is exactly the volume given in the technical characteristics of the hard drive), but this is not entirely true. The fact is that memory is logically divided into buffer memory (Cache) and firmware memory. The processor requires a certain amount of memory to load firmware modules. As far as is known, only Hitachi/IBM indicate the actual volume cache in the description of technical characteristics; relative to other disks, about the volume cache we can only guess.

The next chip is the engine and head unit control controller, or “twist” (Voice Coil Motor controller, VCM controller). In addition, this chip controls secondary power supplies located on the board, which power the processor and preamplifier-switch chip (preamplifier, preamp), located in the hermetic block. This is the main energy consumer on the printed circuit board. It controls the rotation of the spindle and the movement of the heads. Core VCM controller Can work even at temperatures up to 100°C.

Part of the disk firmware is stored in flash memory. When power is applied to the disk, the microcontroller loads the contents of the flash chip into memory and begins executing the code. Without correctly loaded code, the disk will not even want to spin up. If there is no flash chip on the board, it means it is built into the microcontroller.

Vibration sensor (shock sensor) reacts to shaking that is dangerous for the disk and sends a signal about it to the controller VCM. VCM controller immediately parks the heads and can stop the disk from spinning. In theory, this mechanism should protect the disc from further damage, but in practice it does not work, so do not drop the discs. On some drives, the vibration sensor is highly sensitive, responding to the slightest vibration. The data received from the sensor allows controller VCM correct the movement of the heads. At least two vibration sensors are installed on such disks.

There is another protective device on the board - Transient Voltage Suppression (TVS). It protects the board from power surges. During a power surge TVS burns out, creating a short circuit to ground. This board has two TVS, for 5 and 12 volts.

Let's consider the hermetic block.

Under the board there are contacts for the motor and heads. In addition, there is a small, almost invisible hole on the disk body (breath hole). It serves to equalize pressure. Many people believe that there is a vacuum inside the hard drive. Actually this is not true. This hole allows the disc to equalize the pressure inside and outside the containment area. There is a hole on the inside covered with a filter (breath filter), which traps dust and moisture particles.

Now let's take a look inside the containment zone. Remove the disk cover.

The lid itself is nothing interesting. It's just a piece of metal with a rubber gasket to keep out dust.

Let's look at the filling of the containment zone.

Precious information is stored on metal disks, also called pancakes or Pplatters. In the photo you can see the top pancake. The plates are made of polished aluminum or glass and are coated with several layers of different compositions, including a ferromagnetic substance on which the data is actually stored. Between the pancakes, as well as above the top of them, we see special plates called separators or separators (dampers or separators). They are needed to equalize air flows and reduce acoustic noise. As a rule, they are made of aluminum or plastic. Aluminum separators cope more successfully with cooling the air inside the containment zone.

Read-write heads (heads), are installed at the ends of the brackets of the magnetic head unit, or BMG (Head Stack Assembly, HSA). Parking zone- this is the area where the heads of a working disk should be if the spindle is stopped. For this disk, the parking zone is located closer to the spindle, as can be seen in the photo.

On some drives, parking is carried out on special plastic parking areas located outside the plates.

HDD- a precision positioning mechanism and requires very clean air for its normal operation. During use, microscopic particles of metal and grease can form inside the hard drive. To immediately clean the air inside the disc, there is recirculation filter. This is a high-tech device that constantly collects and traps tiny particles. The filter is located in the path of air flows created by the rotation of the plates.

Let's remove the top magnet and see what's hidden underneath.

Hard drives use very powerful neodymium magnets. These magnets are so powerful that they can lift weights up to 1300 times greater than their own. So you should not put your finger between the magnet and metal or another magnet - the blow will be very sensitive. This photo shows the limiters BMG. Their task is to limit the movement of the heads, leaving them on the surface of the plates. BMG limiters Different models are designed differently, but there are always two of them, they are used on all modern hard drives. On our drive, the second limiter is located on the bottom magnet.

Here we see here voice coil, which is part of the magnetic head unit. The coil and magnets form BMG drive (Voice Coil Motor, VCM). The drive and magnetic head unit form positioner (actuator)- a device that moves heads. A black plastic part of complex shape is called actuator latch. This is a defense mechanism that releases BMG after the spindle motor reaches a certain number of revolutions. This happens due to the pressure of the air flow. The lock protects the heads from unwanted movements in the parking position.

Now let's remove the magnetic head block.

Precision and smooth movement BMG supported by precision bearing. Largest part BMG made from aluminum alloy, usually called bracket or rocker (arm). At the end of the rocker there are heads on a spring suspension (Heads Gimbal Assembly, HGA). Usually the heads and rocker arms themselves are supplied by different manufacturers. Flexible Printed Circuit (FPC) goes to the contact pad connected to the control board.

Let's look at the components BMG more details.

A coil connected to a cable.

Bearing.

The following photo shows BMG contacts.

Gasket ensures the tightness of the connection. Thus, air can only enter the unit with discs and heads through the pressure equalization hole. This disc has contacts coated with a thin layer of gold to improve conductivity.

This is a classic rocker design.

The small black parts at the ends of the spring hangers are called sliders. Many sources indicate that sliders and heads are the same thing. In fact, the slider helps to read and write information by raising the head above the surface of the pancakes. On modern hard drives, the heads move at a distance 5-10 nanometers from the surface of the pancakes. For comparison, a human hair has a diameter of about 25000 nanometers. If any particle gets under the slider, this can lead to overheating of the heads due to friction and their failure, which is why cleanliness of the air inside the containment area is so important. The reading and writing elements themselves are located at the end of the slider. They are so small that they can only be seen with a good microscope.

As you can see, the surface of the slider is not flat, it has aerodynamic grooves. They help stabilize the slider's flight altitude. The air under the slider forms air cushion (Air Bearing Surface, ABS). The air cushion maintains the flight of the slider almost parallel to the surface of the pancake.

Here's another slider image

The head contacts are clearly visible here.

This is another important part BMG, which has not yet been discussed. It's called p reamplifier (preamplifier, preamp). Preamplifier- this is a chip that controls the heads and amplifies the signal coming to them or from them.

Preamplifier placed directly in BMG for a very simple reason - the signal coming from the heads is very weak. On modern disks it has a frequency of about 1 GHz. If you move the preamplifier outside the hermetic zone, such a weak signal will be greatly attenuated on the way to the control board.

There are more tracks leading from the preamp to the heads (on the right) than to the containment area (on the left). The fact is that a hard drive cannot simultaneously work with more than one head (a pair of writing and reading elements). The hard drive sends signals to the preamplifier, and it selects the head that the hard drive is currently accessing. This hard drive has six tracks leading to each head. Why so many? One track is ground, two more are for read and write elements. The next two tracks are for controlling mini-drives, special piezoelectric or magnetic devices that can move or rotate the slider. This helps to more accurately set the position of the heads above the track. The last path leads to the heater. The heater is used to regulate the flight altitude of the heads. The heater transfers heat to the suspension connecting the slider and rocker. The suspension is made of two alloys with different thermal expansion characteristics. When heated, the suspension bends towards the surface of the pancake, thus reducing the flight height of the head. When cooled, the gimbal straightens.

If you are a private person, then our specialists will be able to provide widest range of computer services. Our experienced technicians are ready to solve any problem that may arise with your system unit or laptop.

Call:

The quality of the computer services we provide You can rest assured, because we employ experienced and attentive technicians who have been providing computer assistance and computer repairs for many years, of course, using the latest professional equipment.

Join:

Setting up and repairing computers at home - calling a computer technician

Software installation
Motherboard repair
Computer assistance services
Replacing the power supply

Is your computer broken? No problem. Our specialists know how to help you. For computer repairs, we have all the necessary spare parts from certified manufacturers. Home visits are very fast.

Computer help at home 250 rub.

Urgent laptop repair - We save from flooding with liquids and replace parts

Replacing the matrix
Cleaning the keyboard
Replacing the battery
Power supply repair

If your laptop is broken, our experienced technicians will quickly fix it. Even if you accidentally spilled liquid on it and the battery and hard drive burned out, our technicians will quickly return your laptop to working order.

Urgent laptop repair 550 rub.

Removing and treating computer viruses - removing banners

Installing antivirus protection
Treatment of viruses
Removing Trojans
Firewall setup

No computer is immune from malware attacks. Insidious viruses can severely disrupt the operation of your computer and lead to data loss, but our specialists will effectively remove viruses and install anti-virus protection.

Virus removal 270 rub.

Installing and configuring Windows on a computer or laptop

Installing Windows XP, Vista, Seven
Windows setup
Installing drivers
System recovery after a failure

If you do not have the opportunity to install the Windows operating system yourself, just contact our specialists, and they will install any licensed version of Windows and make all the necessary settings.

Windows installation 260 rub.

We save your data - information recovery

From hard drive
After formatting
From a flash drive and memory card
After removal

Regardless of what caused the data loss and on what media this unpleasant phenomenon occurred, our qualified technicians will recover all your data, while maintaining the confidentiality of the files on your computer.

Data recovery 410 rub.

IT services for organizations and subscription services for organizations

Computer administration
Peripheral repair
Information Security
Network configuration

It is difficult to imagine a successful business without well-organized IT services. After all, a lot depends on well-functioning computers and a well-organized data security system. Contact us for IT services - we will not let you down.

HDD, hard drive, hard drive - all these are names for one well-known data storage device. In this material we will tell you about the technical basis of such drives, how information can be stored on them, and other technical nuances and operating principles.

Based on the full name of this storage device - hard magnetic disk drive (HDD) - you can easily understand what underlies its operation. Due to their low cost and durability, these storage media are installed in various computers: PCs, laptops, servers, tablets, etc. A distinctive feature of HDD is the ability to store huge amounts of data while having very small dimensions. Below we will talk about its internal structure, operating principles and other features. Let's get started!

Hermoblock and electronics board

The green fiberglass and copper tracks on it, along with the connectors for connecting the power supply and the SATA socket are called control board(Printed Circuit Board, PCB). This integrated circuit serves to synchronize the operation of the disk with the PC and the management of all processes inside the HDD. The body is made of black aluminum and what is inside it is called sealed block(Head and Disk Assembly, HDA).

In the center of the integrated circuit there is a large chip - this microcontroller(Micro Controller Unit, MCU). In today's HDDs, the microprocessor contains two components: central computing unit(Central Processor Unit, CPU), which handles all calculations, and read-write channel- a special device that converts an analog signal from the head to a discrete one when it is busy reading and vice versa - digital to analog during writing. The microprocessor has I/O ports, with the help of which it controls the remaining elements located on the board and exchanges information via a SATA connection.

The other chip located on the circuit is a DDR SDRAM memory chip. Its quantity determines the size of the hard drive cache. This chip is divided into firmware memory, partially contained in a flash drive, and a buffer memory, necessary for the processor to load firmware modules.

The third chip is called motor and head controller(Voice Coil Motor controller, VCM controller). It controls additional power supplies that are located on the board. They provide power to the microprocessor and preamplifier-switcher(preamplifier) contained in a sealed unit. This controller requires more power than other components on the board, as it is responsible for spindle rotation and head movement. The preamplifier-switcher core is capable of operating at temperatures up to 100°C! When power is supplied to the HDD, the microcontroller unloads the contents of the flash chip into memory and begins executing the instructions stored in it. If the code fails to load properly, the HDD will not even be able to spin up. Also, flash memory can be built into the microcontroller rather than contained on the board.

Located on the diagram vibration sensor(shock sensor) detects the level of shaking. If he considers its intensity dangerous, a signal will be sent to the motor and head controller, after which it immediately parks the heads or completely stops the rotation of the HDD. In theory, this mechanism is designed to protect the HDD from various mechanical damage, however, in practice it does not work out very well. Therefore, you should not drop the hard drive, because this can lead to inadequate operation of the vibration sensor, which can cause the device to become completely inoperable. Some HDDs have sensors that are ultra-sensitive to vibration and respond to the slightest manifestation of vibration. The data that VCM receives helps in correcting the movement of the heads, so the disks are equipped with at least two such sensors.

Another device designed to protect the HDD is transient voltage limiter(Transient Voltage Suppression, TVS), designed to prevent possible failure in the event of voltage surges. There may be several such limiters on one circuit.

HDA surface

Under the integrated board there are contacts from motors and heads. Here you can see an almost invisible technical hole (breath hole), which equalizes the pressure inside and outside the sealed zone of the block, destroying the myth that there is a vacuum inside the hard drive. Its internal area is covered with a special filter that does not allow dust and moisture to pass directly into the HDD.

The insides of the HDA

Under the cover of the sealed unit, which is an ordinary layer of metal and a rubber gasket that protects it from moisture and dust, there are magnetic disks.

They may also be called pancakes or plates(platters). The discs are usually created from glass or aluminum that has been pre-polished. Then they are covered with several layers of various substances, including a ferromagnet - thanks to it it is possible to record and store information on a hard drive. Between the plates and above the topmost plate are located separators(dampers or separators). They even out air flows and reduce acoustic noise. Usually made of plastic or aluminum.

Separator plates, which were made of aluminum, do a better job of lowering the air temperature inside the sealed zone.

Magnetic head block

At the ends of the brackets located in magnetic head block(Head Stack Assembly, HSA), read/write heads are located. When the spindle is stopped, they should be in the preparation area - this is the place where the heads of a working hard drive are located when the shaft is not working. In some HDDs, parking occurs on plastic preparation areas that are located outside the platters.

For normal operation of a hard drive, air that is as clean as possible, containing a minimum of foreign particles, is required. Over time, microparticles of lubricant and metal form in the storage tank. To output them, HDDs are equipped circulation filters(recirculation filter), which constantly collects and retains very small particles of substances. They are installed in the path of air flows that are formed due to the rotation of the plates.

Neodymium magnets are installed in HDDs, capable of attracting and holding weight that can be 1300 times more than its own. The purpose of these magnets in HDDs is to limit the movement of the heads by holding them above plastic or aluminum plates.

Another part of the magnetic head block is coil(voice coil). Together with magnets it forms BMG drive, which together with BMG makes up positioner(actuator) - a device that moves heads. The protection mechanism for this device is called retainer(actuator latch). It releases the BMG as soon as the spindle reaches a sufficient number of revolutions. Air flow pressure is involved in the release process. The clamp prevents any movement of the heads in the preparation state.

There will be a precision bearing under the BMG. It maintains the smoothness and precision of this block. There is also a part made of aluminum alloy called rocker(arm). At its end, on a spring suspension, there are heads. It comes from the rocker flexible cable(Flexible Printed Circuit, FPC) leading to a pad that connects to the electronics board.

This is what the coil looks like when connected to the cable:

You can see the bearing here:

Here are the BMG contacts:

Pad(gasket) helps ensure the tightness of the clutch. Thanks to this, air enters the block with disks and heads only through an opening that equalizes the pressure. The contacts of this disk are coated with the finest gold plated, which improves conductivity.

Typical bracket assembly:

At the ends of the spring hangers there are small-sized parts - sliders(sliders). They help read and write data by raising the head above the platters. In modern drives, the heads operate at a distance of 5-10 nm from the surface of metal pancakes. Elements for reading and writing information are located at the very ends of the sliders. They are so small that they can only be seen using a microscope.

These parts are not completely flat, as they have aerodynamic grooves on them that serve to stabilize the flight altitude of the slider. The air underneath creates pillow(Air Bearing Surface, ABS), which maintains flight parallel to the surface of the plate.

Preamplifier- a chip responsible for controlling the heads and amplifying the signal to or from them. It is located directly in the BMG, because the signal produced by the heads has insufficient power (about 1 GHz). Without the amplifier in a sealed area, it would simply dissipate on its way to the integrated circuit.

From this device there are more paths towards the heads than towards the sealed area. This is explained by the fact that the hard drive can only interact with one of them at a certain point in time. The microprocessor sends requests to the preamplifier so that it selects the head it needs. From the disk to each of them there are several tracks. They are responsible for grounding, reading and writing, controlling miniature drives, working with special magnetic equipment that can control the slider, which allows increasing the accuracy of the heads. One of them should lead to a heater that regulates their flight altitude. This design works like this: heat is transferred from the heater to the suspension, which connects the slider and the rocker. The suspension is created from alloys that have different expansion parameters from the incoming heat. As the temperature rises, it bends towards the plate, thereby reducing the distance from it to the head. When the amount of heat decreases, the opposite effect occurs - the head moves away from the pancake.

This is what the top separator looks like:

This photo shows the sealed area without the head assembly and upper separator. You can also notice the bottom magnet and clamping ring(platters clamp):

This ring holds the blocks of pancakes together, preventing any movement of them relative to each other:

The plates themselves are strung on shaft(spindle hub):

And here's what's under the top plate:

As you can understand, the space for the heads is created using special spacer rings(spacer rings). These are high-precision parts that are made from non-magnetic alloys or polymers:

At the bottom of the HDA there is a pressure equalization space located directly below the air filter. The air that is outside the sealed unit certainly contains dust particles. To solve this problem, a multilayer filter is installed, which is much thicker than the same circular one. Sometimes you can find traces of silicate gel on it, which should absorb all the moisture:

Conclusion

This article provided a detailed description of the internals of the HDD. We hope this material was interesting to you and helped you learn a lot of new things from the field of computer equipment.

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!

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

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

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

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

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

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

An important fact is that the HDD memory is not volatile, that is, no matter whether the power is connected or not, the information recorded on the device will not disappear anywhere. This 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 (in budget options) to several;
Engine — on the spindle of which the pancakes are fixed;
Head block - a design of interconnected levers (rocker arms) and heads. The part of the hard drive that reads and writes information to it. For one pancake, a pair of heads is used, since both the upper and lower parts are working;
Positioning device (actuator ) - a mechanism that drives the head block. Consists of a pair of permanent neodymium magnets and a coil located at the end of the head block;
Controller — an electronic microcircuit that controls the operation of the HDD;
Parking zone - a place inside the hard drive next to the disks or on their inner part, where the heads are lowered (parked) during downtime, so as not to damage the working surface of the pancakes.

This is 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 of the magnetic plates to the heads is so small (~10 nm) that you cannot see it with the naked eye.

After startup, first of all, service information about the state of the hard disk and other necessary information about it, located on the so-called zero track, is read. 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 hard drive manufacturers on the market: Western Digital (WD), Toshiba, Seagate. They fully cover the demand for devices of all types and requirements. The rest of the companies either went bankrupt, 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 drives 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 drive. 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 a 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:

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.

), information in- shortened name for " Hard Disk Storage". You will also find English Hard Disk Drive- and slang Winchester or for short Screw.

In a computer, the hard drive is responsible for storing data. The Windows operating system, programs, movies, photos, documents, all the information that you download to the computer is stored on the hard drive. And the information on a computer is the most valuable thing! 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)

I also suggest watching an excerpt from a Discovery Channel program 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 does not have enough fast RAM to run a program, it uses up space on the 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. In this case, the magnetic heads “float” above the disk in the air flow created by the rotating disk. The distance between the disk and the 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 the working area and shock overloads are not so terrible for the 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 an additional hard drive or replacing the old one with a larger one, what will you need to know when purchasing?

First, look under the cover of your computer's system unit. You need to find out which hard drive interface the motherboard supports. Today the most common standards are 3.5 inch and moribund IDE. They are easy to distinguish by their 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 3.5 inch. They differ in data transfer speed. 3.5 inch, SATA II And SATA III at speeds of 1.5, 3 and 6 gigabytes per second, respectively. All interface versions 3.5 inch 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, to record high quality video. Modern films in HD format reach several tens of gigabytes.

In addition, the main parameters include:

Form factor- disk size. 1.8 and 2.5 inch drives are used in laptops. For a 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 disks 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 of their reduced power 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 an increased reliability life, but they are also much more expensive than regular ones.
Manufacturer. There are currently several large manufacturers on the storage drive market. 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.