What is HDD (Hard Disk Drive)? What is HDD, hard disk and hard drive What does hdd mean in a computer.

We, users of a personal computer, often come across the abbreviation HDD. And the desire to find out what HDD is, where it is and why it is needed is justified.

HDD stands for "hard disk drive". Simply put, it's a hard drive. Gradually receding into the past, they are supplanted by SSDs, but they will occupy their niche in the HDD market for a long time.

Why is the disk "hard"

HDD in the computer is not named. Hard drive, hard drive, hard drive, screw - just a small list of his names. Why "hard disk drive" anyway?

Unlike "floppy" disks (floppy disks), data on HDDs is recorded on hard plates, and they, in turn, are covered with a layer of ferromagnetic material. They are called nothing other than "magnetic disks". A hard disk uses one or more platters on one axis. The reading devices (heads) do not touch the surface of the plates during operation. The explanation is simple: with the fast rotation of the plates, an interlayer of the incoming air flow is formed. The distance between the reader and the working surface is very small - only a few nanometers, and an air layer that excludes mechanical contact ensures a long service life. If the plates do not rotate at the proper speed, then the heads are in the so-called "parking" zone - outside the boundaries of the plates.

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

Main characteristics of HDD

Like any technical device, a hard disk has a number of characteristics, based on which conclusions can be drawn about its relevance.

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

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

Many of you know that all information on a computer, presented in the form of files and folders, is stored on the hard disk. And here, what is hard drive and what it is intended for, not many will answer correctly. It is very difficult for people far from programming to imagine how information can be stored on some piece of iron. After all, this is not a box or a sheet of paper on which this very information can be written down and hidden in the box. Yes, a hard drive is not a box with a letter.

A hard disk (HDD, HMDD-from English hard (magnetic) disk drive) is a magnetic storage medium. In computer slang, it is called "Winchester". It is designed to store information in the form of photographs, pictures, letters, books of various formats, music, films, etc. Outwardly, this device does not look like a disk at all. Rather, it looks like a small rectangular iron box.

The internal structure of a hard drive looks like an old turntable.

Inside this metal box there are round aluminum or glass disc plates located on the same axis along which the reading head moves. Unlike a turntable, the hard disk head does not touch the surface of the platters during operation.

For convenience, the hard drive is divided into several sections. This division is conditional. This is done using the operating system or special programs. New partitions are called logical drives. They are assigned the letters C, D, E or F. Usually installed on drive C, and files and folders are stored on other drives so that your files and folders will not be damaged during a system crash.

Watch a video on what a hard drive is:

Main characteristics of hard drives

• Form factor Is the width of the hard drive in inches. Standard size for desktop is 3.5 "and for laptops 2.5";
• Interface- modern computers use various versions of SATA motherboard connections. SATA, SATA II, SATA III. Older computers use the IDE interface.
• Capacity- This is the maximum amount of information that a hard drive can store, measured in gigabytes;
• Spindle speedIs the number of spindle revolutions per minute. The higher the rotational speed of the disk, the better. For operating systems, it is necessary to install disks from 7,200 rpm and higher, and to store files, you can install disks at a lower speed.
• MTBFIs the manufacturer's calculated MTBF. The bigger it is, the better;
• Random access timeIs the average time required for the head to position on an arbitrary section of the plate. The quantity is not constant.
• Shock resistanceIs the ability of a hard drive to withstand pressure changes and shocks.
• Noise level,which the disc emits during operation, measured in decibels. The smaller it is, the better.

Now there are already SSDs (solid-state drives in a simple translation - solid-state drive), which do not have a spindle or platters. It is a storage device based on memory chips.

SSDs are completely quiet and have very good read and write speeds. But they are still very expensive and not very reliable, so they are installed only for operating systems, and IDE and SATA hard drives are used to store files.

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

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

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

Let's consider this box in more detail.

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

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

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

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

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

Figure 1. Simplified diagram of a circular hard drive

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

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

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

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

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

Hard drive specifications

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

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

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

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

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

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

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

This article will only talk about hard disks (HDD), that is, about media on magnetic disks. The next article will be about SSD.

What is a hard drive

Traditionally, let's take a look at the definition of a hard drive on Wikipedia:
Hard disk (screw, hard drive, hard disk drive, hard disk drive, HDD, HMDD) is a random access memory device based on the principle of magnetic recording.
They are used in the vast majority of computers, as well as separately connected devices for storing backup copies of data, as file storage, etc.
Let's figure it out a bit. I like the term "hard disk drive". These five words convey the whole point. HDD is a device whose purpose is to store data recorded on it for a long time. HDD is based on hard (aluminum) disks with a special coating, onto which information is recorded using special heads.
I will not consider in detail the recording process itself - in fact, this is the physics of the last grades of school, and I'm sure you have no desire to delve into this, and the article is not about that at all.
Let's also pay attention to the phrase: "random access" which, roughly speaking, means that we (the computer) can read information from any section of the railway at any time.
It is important that the HDD memory is not volatile, that is, it does not matter whether the power is connected or not, the information recorded on the device will not disappear anywhere. This is an important difference between permanent computer memory and temporary memory (RAM).
Looking at a computer's hard drive in real life, you will not see any disks or heads, since all this is hidden in a sealed case (hermetic zone). Externally, the hard drive looks like this.
I think you understand what HDD is. Move on.

Why does a computer need a hard drive

Consider what is HDD in a computer, that is, what role it plays in a PC. It is clear that it stores data, but how and what. Here we highlight the following functions of the hard drive:
- Storage of OS, user software and their settings;
- User files storage: music, video, images, documents, etc;
- Using part of the hard disk space to store data that does not fit in RAM (paging file) or storing the contents of RAM during sleep mode;
“As you can see, a computer's hard drive is not just a dump of photos, music and videos. The entire operating system is stored on it, and in addition to this, the hard disk drive helps to cope with the RAM load, taking on some of its functions.

What does a hard drive consist of?

We partially mentioned about the composite hard disk, now we will deal with this in more detail. So, the main components of the HDD:
- Case - protects the hard drive mechanisms from dust and moisture. As a rule, it is sealed so that the very moisture and dust do not get inside;
- Discs (pancakes) - plates made of a certain alloy of metals, coated on both sides, on which data is recorded. The number of plates can be different - from one (in budget versions) to several;
- Engine - on the spindle of which pancakes are fixed;
- Block of heads - a structure of interconnected levers (rocker arms), and heads. Part of the hard disk drive that reads and writes information to it. For one pancake, a pair of heads is used, since both the upper and lower parts are working;
- Positioning device (actuator) - a mechanism that drives the head block. Consists of a pair of permanent neodymium magnets and a coil at the end of the head block;
- Controller - an electronic microcircuit that controls the operation of the HDD;
- Parking area - a place inside the hard drive next to the disks or on their inside, where the heads are lowered (parked) during idle time so as not to damage the working surface of the pancakes.
Such is the simple device of the hard disk. It was formed many years ago, and no fundamental changes have been made to it for a long time. And we move on.

How a hard drive works

After the power is supplied to the HDD, the engine, on the spindle of which the pancakes are fixed, begins to spin. Having gained the speed at which a constant air flow is formed at the surface of the disks, the heads begin to move.
This sequence (first, the discs spin, and then the heads start to work) is necessary so that due to the formed air flow, the heads float above the plates. Yes, they never touch the surface of the discs, otherwise the discs would be instantly damaged. However, the distance from the surface of the magnetic plates to the heads is so small (~ 10 nm) that you cannot see it with the naked eye.
After starting, first of all, it reads service information about the state of the hard disk and other necessary information about it, located on the so-called zero track. Only then does the work with data begin.
Information on the computer's hard disk is recorded on tracks, which, in turn, are divided into sectors (a kind of pizza cut into pieces). To write files, several sectors are combined into a cluster, which is the smallest place where a file can be written.
In addition to this "horizontal" partitioning of the disk, there is also a conditional "vertical". Since all heads are combined, they are always positioned above the same track number, each above its own disc. Thus, during the operation of the HDD, the heads seem to draw a cylinder.
While the HDD is running, it essentially performs two commands: read and write. When it is necessary to execute a write command, the area on the disk where it will be performed is calculated, then the heads are positioned and, in fact, the command is executed. Then the result is checked. In addition to writing data directly to the disk, information also goes to its cache.
If the controller receives a command to read, the first thing to check is the presence of the required information in the cache. If it is not there, the coordinates for positioning the heads are calculated again, then the heads are positioned and the data is read.
After completion of work, when the power supply to the hard drive disappears, the heads are automatically parked in the parking zone.
This is, in general terms, how a computer's hard drive works. In reality, everything is much more complicated, but an ordinary user, most likely, does not need such details, so we will finish with this section and move on.

Types of hard drives and their manufacturers

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

1. For laptops - the main parameter is the device size of 2.5 inches. This allows them to be compactly located in the laptop case;
2. For PC - in this case it is also possible to use 2.5 "hard drives, but as a rule, 3.5" are used;
3. External hard drives - devices that are separately connected to a PC / laptop, most often acting as a file storage.
There is also a special type of hard drives for servers. They are identical to conventional PCs, but may differ in connection interfaces and higher performance.

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

Hard drive specifications

So, the main characteristics of a computer hard drive:

Volume is a measure of the maximum amount of data that can be stored on a disk. The first thing to look at when choosing an HDD. This figure can reach 10 TB, although 500 GB - 1 TB is more often chosen for a home PC;
- Form Factor - The 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 on the PC and on the server. The form factor also affects the volume, since a larger disk can fit more data;
- Spindle speed - how fast the pancakes rotate. The most common are 4200, 5400, 7200 and 10000 rpm. This characteristic directly affects the performance, as well as the price of the device. The higher the speed, the higher both values;
- Interface - a method (connector type) of connecting the HDD to a 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 size (cache memory) - the type of fast memory (by the type of RAM) installed on the hard disk drive controller, designed for temporary storage of the most frequently accessed data. The buffer size can be 16, 32 or 64 MB;
- Random access time - the time during which the HDD is guaranteed to perform writing or reading from any part of the disk. Fluctuates from 3 to 15 ms;

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

Data transfer rate;
- The number of input-output operations per second;
- Noise level;
- Reliability;
- Resistance to shocks, etc .;
That's all about the characteristics of the HDD.

Good day to all, my dear friends and readers. A friend of mine told me that when he was still working in a video salon, a grandmother of 70-80 years old came to him. She went up to a friend and said that she needed "HADEDE". A friend did not seem to immediately understand and asked again, they say, hadde? She repeated it once more, but when she saw that her friend wasn’t eating, she took out a piece of paper and said that her grandson had told her to buy HADEDE.

HDD 160 GB was written on that piece of paper. Well, a friend chuckled and said that it was a hard drive for a computer and sent them to another store. But this is no longer surprising. How could a granddaughter even send his grandmother for a hard drive? Well, has it collapsed from an oak tree?

But what am I getting at? Let me tell you all the same what HDD is in a computer. Then you will definitely have no questions if you want to buy it yourself.

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

A hard disk is a long-term source of memory and after a power outage, all information remains on it, in contrast to fast RAM. Therefore, you can always store your files, photos, music, etc. on it. But of course this is a device, so do not forget about for greater security.

The theory of the origin of the name "Winchester"

I already hear the question “Why is it called a hard drive? These are small arms! " Indeed, what can a storage device and a gun have in common? The fact is that in 1973 the notorious IBM company released the 3340 hard drive, but for consonance it was called simply "30-30", which meant two modules of 30 megabytes each.

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

For convenience, it was decided to use this name as slang. True, Americans have not used this slang for a long time, and we have not yet gone out of use, although more often it can be heard in the abbreviated name "Screw".

Hard disk device

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

And this work is somewhat similar to the work of a turntable, only the reader without a needle does not touch the magnetic disks, although the distance between them is simply negligible.

Main characteristics of hard drive

Volume

The size of your hard disk determines how much information you can store on it. Over time, the size of memory on new hard drives increases, as there is a real need for it. If on my first computer the volume was 40 GB and it was enough for me, now I have 2000 GB on my computer and I have already scored half. Of course, some can be removed without tears).

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

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

But after all, 1 GB is actually not 1000, but 1024 MB, just like 1 MB is not 1000, but 1024 KB. As a result, it turns out that we divide 500 million by 1024, and then another by 1024 and get our 476 GB with kopecks. I have about 140 GB on a disk of 2 Terabytes. Nice, huh? In general, now you will know.

Rotational speed

Hard disk performance is also determined by the spindle speed. And the higher this speed, the greater the disk performance, but the more power consumption is required and the greater the likelihood of failure.

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

On stationary computers, in most cases, hard drives are set at a speed of 7200 rpm. Here it is really profitable, since inpatients, as a rule, there is more powerful equipment that can work at such a speed. Plus, the computer is constantly connected to the outlet, which means there will be no power shortage.

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

Connection interface

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

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

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

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

There are other interfaces, for example SCSI or SAS, but these are no longer mandatory standards for easy use.

Form factor

I was asked here recently, what is the form factor for hard drives? Everything is simple here. These are just its dimensions. Distinguish between 2.5 and 3.5 inches. There are others, of course, but no one uses them in everyday life or they are out of date.

A 2.5 "hard drive will be inserted into laptops, and 3.5" into stationary computers. I think that you will not confuse anything)

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

Best regards, Dmitry Kostin.