What the hard drive contains. What is HDD, hard drive and hard drive

19:20 28.04.2001

A Dummies' Guide to Choosing Hard Drives Introduction

A lot depends on which hard drive you install in your system unit. First of all, the performance of your system. It should be borne in mind that installing a modern hard drive in old model a computer is not advisable. The performance will be limited by the speed of the old protocols, and the disk will only work "half-heartedly". Building such systems is a waste of money. Professional computer builders call these "unbalanced solutions". I'll make a reservation that buying components with a stock for the next upgrade has nothing to do with these cases.

When buying a new hard drive, it's worth deciding what you are using your computer for. This question is worth asking yourself with any upgrade and not just a hard drive. Note that for a video editing station and for a system for working with databases, absolutely different are needed. hard drives... What should you look for when making a purchasing decision? First of all, the size of the files you have to work with. When working with small files, it is worth taking a disk with a large volume of the built-in cache. If you are a real professional, then it is worth "overlaying" these "sizes" on the file system type.

It is also important to find out the exact markings on the motherboard. Based on this data, you can find out which chipset is at its core. As a rule, the task comes down to the exact definition of marking south bridge... It is he who is responsible for the connection between the processor and the hard drive and its parameters will allow you to purchase a hard drive that is as balanced as possible with your system.

In this article, we are going to walk you through the main interfaces of hard drives. We will give information that will teach you to read the name of the hard drives. And also we will give the characteristics of the most popular hard drives.

Interface

Now you can buy a hard drive of almost any interface. However, we will limit ourselves to talking about only two of them - IDE and SCSI. You will have to pay attention to them when buying. Hard drives with other interfaces are too expensive and are not widely used in home and office solutions.

So the IDE types (sorted in order of appearance):

  • regular IDE or ATA (Advanced Technology Attachment- device with built-in controller)
  • EIDE (Enhanced IDE) or ATA-2
  • ATAPI
  • Ultra ATA (ATA-33, ATA-66, ATA-100)

A few words about ATAPI (ATA Packet Interface). This interface is used for devices such as CDROMs, streamers, etc. So, most likely, when buying a hard drive, you will not hear this abbreviation. However, like EIDE and just IDE. Now on the shelves of computer stores there are Ultra DMA-66 and Ultra DMA-100 disks, a little less often you can find Ultra DMA-33. The last two digits show the data transfer rate in megabytes per second (for example, 33 MB / s). There are several ways IDE connections hard drive to your computer. First of all - the most popular - by means of a 40- or 80-wire cable (AT-BUS interface type). I would like to emphasize that the cable length should not be more than 43 cm. Otherwise, the stable operation of the device is not guaranteed, and some data may be lost. To implement Ultra DMA-66 and Ultra DMA-100, you need exactly an 80-core cable. If you use a 40-wire cable with such drives, the bus speed will be only 33 MB / s.

What is the difference between Ultra DMA-33, Ultra DMA-66, and Ultra DMA-100? The numbers at the end indicate the maximum bus data transfer rate (Mb / s) from the disk controller to the motherboard. Note that the actual data transfer rate can be significantly lower. It depends on the speed of the disk, the speed of the electronics, the operation of the memory and the processor. When you upgrade yourself, it is not uncommon for an inexperienced user to start "pushing" the hard drive cable into the drive slot. This procedure leads to broken contacts. It is extremely problematic to restore them later. Check out what the 40-pin IDE connector looks like:

And never confuse it with the 34-pin FDD connector, here it is:

The second type of connection is called PC Card ATA. It is implemented using a PC Card (PCMCIA), has a 16-bit interface. This type is mainly used in portable computers (laptops).

Hard drives have different on-board cache sizes and different spindle rpm values. The cache noticeably affects the speed of working with data, especially when working with small files without data, when information is updated "locally" and occurs quite often (for example, work on entering accounting data). The cache size for modern disks ranges from half a megabyte to two megabytes. Sometimes even professionals find it difficult to decide how much cache is optimal for a given system. You can be guided by the principle - "more is better than less."

The number of spindle revolutions is directly related to the rotation of the storage media - disks. Of course, this parameter affects the amount of data read per unit of time. Discs with rotation speeds of up to 10,000 (not yet commercially available) rpm are available on the market, however, among them the more common 5400 and 7200 rpm. Discs "5400" are more reliable and durable. When working, they heat up less. "7200", as a rule, are noisier and less durable, but the speed characteristics of such solutions are higher. In this case, you have to choose. Below we will talk about some of the models, and you can compare all of the above with examples.

IDE hard drives are the cheapest on the market. The low cost is due to the high integration of the device. The controller and the recorder itself are assembled in one housing. The reliability of such hard drives is quite high. For home users, choosing a hard drive usually comes down to deciding which model of IDE device to buy.

Finally, a few words about how IDE devices are connected. A maximum of two devices can be connected to one IDE cable. One of the devices must be set to Master mode, and the other to Slave. Setting the modes is carried out by setting jumpers on the devices themselves. All modern IDE devices usually have a jumper setting table. If you have two hard drives, then the system will only boot from the Master device. Usually, the slave mode is not allowed in the absence of a master. but modern drives and the BIOS allows this to work.

SCSI is a less popular interface than IDE (mainly due to its relative high cost).

  • SCSI-1: 8-bit data bus, maximum transfer rate up to 5 MB / s, 25- or 50-pin connector;
  • SCSI-2 or Fast SCSI (Fast SCSI): 8-bit data bus, maximum transfer rate - up to 10 MB / s, 50-pin connector; the connector looks like this:
  • Wide SCSI: 16-bit data bus, maximum baud rate up to 20 MB / s, 68- or 80-pin Single Connector that combines power and signal circuits
  • Ultra SCSI / Ultra Wide SCSI or SCSI-3: 8/16-bit data bus, maximum transfer rate up to 20/40 MB / s, 50-, 68-, or 80-pin Single Connector that combines power and signal circuits ;
  • Ultra2 SCSI: 16-bit data bus, maximum baud rate up to 80 MB / s, 68- or 80-pin Single Connector, combining power and signal circuits; the connector looks like this:

This interface is not only intended for use with hard drives. The controller, which is inserted into a separate slot on the motherboard, can support up to 15 different devices (scanners, CD-ROMs, hard drives, etc.). The cable length can be up to 15 meters. This gives the system a certain amount of flexibility, however, for the home user this is not an important selection criterion.

Manufacturers of SCSI hard drives have developed devices with a disk rotation speed of 15,000 rpm. The speed characteristics of such hard drives easily beat the fastest IDE drives.

The SCSI controller is not difficult to buy, but it is quite expensive, however, like the disks of this interface themselves. In any case, it is worth buying only modern solutions, and in our country they belong to the "hi-end" market. Therefore, I would recommend SCSI hard drives only for those users who are engaged in serious video editing or need systems where it is necessary to use a large number of hard drives ...

The main advantage of SCSI for home use is its low processor load and higher operating speed.

In this article, I will only talk about IDE hard drives. In the overwhelming majority of cases, it is them that the user buys due to their low cost. If in the future there is an interest in SCSI hard drives, then we will devote a separate article to this.

Hard drive markings

When a hard drive falls into your hands, starting to turn it, you notice a rather large inscription of numbers and letters on its case. This is the brand name of the hard drive (alphanumeric code). Unfortunately, there is no single system (standard) for applying this inscription. Each manufacturer does it differently. To my even greater regret, some manufacturers periodically move away from their labeling and come up with a new standard for an alphanumeric code.

Quite a long time ago I found descriptions of markings of most manufacturers in the vastness of the network. Since then, I have used this information with varying degrees of success. These data are:

    <Обозначение фирмы><Форм-фактор><Форматированный объем><Тип интерфейса>
  • Company designation: ST
  • Form Factor: 1 = 3.5 "x 41 mm; 3 = 3.5" x 25 mm; 4 = 5.25 "x 82 mm; 5 = 3.5" x 19 mm; 9 = 2.5 "
  • Formatted size: the size of the hard drive in MB. The last digit shows the development number.
  • Interface type: A = ATA (IDE); DC = SCSI 16 bit Single Connector Differential; FC = Fiber Channel; LC = SCSI 16 bit Single Connector Low Voltage Differential; LW = SCSI 16 bit Low Voltage Differential; N = SCSI 8 bit; ND = SCSI 8 bit Differential; W = SCSI 16 bit; WC = SCSI 16 bit Single Connector; WD = SCSI 16 bit Differential

Western digital

    <Обозначение фирмы><Тип интерфейса><Модель><Количество дисков><Форматированный объем><Светодиодный индикатор><Пеpедняя панель><Объем кэша>
  • Company designation: WD
  • Interface type: A = IDE; S = SCSI; C = PCMCIA-IDE;
  • Model: C = Caviar; P = Piranha; L = Lite; U = Ultralite;
  • LED indicator: 0 = no; 1 = red; 2 = green
  • Front panel: 0 = no; 1 = black; 2 = gray
  • Buffer size: no data

IBM

    <Тип устройства><Модель><Тип интерфейса><Форм-фактор><Форматированный объем>
  • Device type: D - hard drive
  • Interface type: A = ATA (IDE); S = SCSI; C = Serial Storage Architecture (SSA)
  • Form Factor: 2 = 2.5 "; 3 = 3.5"
    <Обозначение фирмы><Модель><Форматированный объем><Тип интерфейса>
  • Interface type: A - ATA (IDE); S - SCSI; V - Value

Fujitsu

    <Модель><Тип интерфейса><Размер блока><Тип резьбы винтов>
  • Interface type: T = ATA (EIDE); S = SCSI; SY = Fast SCSI-2 (Ultra); H = SCSI, differential; Q = Wide SCSI; R = Wide SCSI, differential; C = Wide SCSI, SCA-1; E = Wide SCSI, SCA-2;
  • Block size: A = 512 bytes; X = 256 bytes; B = 1024 bytes;
  • Screw thread type: M = metric M3; U = # 6-32 UNC.

So, let's move on to the description of specific models of hard drives that you can purchase in computer stores.

IBM 75GXP

Models of hard drives from IBM are well-deservedly popular in our country and all over the world. However, the latest DTLA series of hard drives turned out to be not very reliable. The number of defects in it forced IBM itself to abandon the further release of these models. Nevertheless, these hard drives will remain in stores for a long time and will be in good demand due to the highest speed characteristics.

The company has two assembly plants in Hungary and Taiwan. I like the models assembled in Taiwan more, because the compatibility problems of these devices are much less. Hard drives assembled in Hungary are as reliable as Taiwanese devices. But the compatibility of these hard drives is much worse.

Below is a table in which you can see all models of hard drives from the IBM Deskstar family. (the popular DTLA hard drive appeared in this family). It is very clearly seen how the size of the built-in cache grows and the spindle "picks up speed".

Model name Device capacity Interface Built-in cache size Rotational speed
DSAA 270 to 720 MBytes PIO3 96 KB 4500 revolutions per second
DPEA from 540 to 1080 Mb PIO3 96 KB 5400 revolutions per second
DJAA 1.2 and 1.7 GB PIO4 96 KB 4500 revolutions per second
DAQA from 2.1 to 3.2 GB PIO4 128 KB 5400 revolutions per second
DCAA 3.6 and 4.3 GB PIO4 96 KB 5400 revolutions per second
DHEA from 4.3 to 8.4 GB UltraATA / 33 476 KB 5400 revolutions per second
DTTA 16GP from 3.2 to 16.8 GB UltraATA / 33 512 KB 5400 revolutions per second
DTTA 14GXP from 10 to 14.4 GB UltraATA / 33 512 KB 7200 revolutions per second
DJNA 25GP from 10 to 25 GB UltraATA / 33 512 KB or 2048 KB 5400 revolutions per second
DJNA 22GXP from 9 to 22 GB UltraATA / 66 2048 KB 7200 revolutions per second
DPTA 37GP from 15 to 37 GB UltraATA / 66 512 KB or 2048 KB 5400 revolutions per second
DPTA 34GXP from 13 to 34 GB UltraATA / 66 2048 KB 7200 revolutions per second
DTLA 40GV from 20 to 40 GB UltraATA / 100 512 KB 5400 revolutions per second
DTLA 75GXP from 15 to 75 GB UltraATA / 100 2048 KB 7200 revolutions per second

Let's see what the technical characteristics of the latest hard drive of this family are:

IBM Deskstar 75GXP
Device volume 15, 20, 30, 45, 60, 75 GB
RPM speed 7200 revolutions per second
Average access time 8.5 ms
Built-in cache size 2048 Kb
Factory warranty 3 years

As you can see, these hard drives have the best (largest) values ​​for cache and "responsiveness". I would recommend such a hard drive for those users who are ready to give up everything for the sake of speed. Tests show that this hard drive has no equal. It should be borne in mind that during their work, modern IBM hard drives make a lot of noise. And due to the high rotational speed, the surface of the hard drive case gets very hot. Therefore, it is worth stocking up on a good case or even installing an additional cooling system. It costs about $ 15 (not every system unit is suitable for installing it). The reliability of this hard drive is poor. It is difficult to unambiguously isolate the cause of the failures, since everything breaks down. There are a lot of defects among 30 GB models. The cost of these hard drives is noticeably higher than all other competitors. In other words, it is more expensive than its counterparts by $ 30-60.

Fujitsu MPF-3204AH

Fujitsu is famous for its traditionally reliable and inexpensive solutions. Recently, she has created several "fast" discs. Among them is the Fujitsu MPF-3204AH ATA-100 model. It has a working volume of 20 GB. The company produces AH hard drives of a different volume, but it is practically impossible to purchase them on the retail market.

Here are the technical characteristics of the Fujitsu MPF-3204AH model:

Fujitsu MPF-3204AH
Device volume 20.4 GB
RPM speed 7,200 revolutions per second
Average access time 8.5 ms
Built-in cache size 2048 Kb
Warranty 3 years
As you can see in its characteristics the disk is not inferior to the previous IBM model. But in the speed of real work, he loses. However, in my opinion, this is more than offset by the reliability and speed of the drive. The hard drive has a very sturdy box. By the way, it is she who makes Fujitsu MPF-3204AH one of the quietest hard drives. Take a look at the cross-section of this hard drive:

When working with hard drives from this company, there are never any installation problems. Since the information about the position of the jumpers is always present on the housing cover. This is done in a large and legible manner. Take a look at an example:

Despite the high rotation speed of the spindle, the disc does not heat up significantly during its operation. Affected by the excellent bearing system.

I have not encountered or heard of Fujitsu MPF-3204AH compatibility issues. The cost of the model is relatively low, and it seems to me that this hard disk model can become a leader in the price / reliability and price / performance ratio.

Seagate has long ceased to be the leader in the IDE hard drives market, but in the SCSI segment it firmly holds the leading position. The company makes very reliable hard drives. Some users who use drives to transfer large amounts of information buy Seagate products on purpose (although I do not recommend doing so).

The speed of these drives is poor. Although the average access time declared by the manufacturer is very short, the real time for searching and positioning the head is quite long. But if the file is located very tightly (no defragmentation), then its read speed (linear read speed) is not inferior to the IBM models.

Here are the brief technical specifications for this hard drive:

Seagate Barracuda ATA, ST320430A
Device volume 20.4 GB
RPM speed 7,200 revolutions per second
Average access time 7.6 ms
Built-in cache size 512 Kb
Warranty 3 years

Thanks to the iron casing, the disc makes little noise. Although, when working with defragmented data, strange "squeals" are heard. On the back of the disk there is an instruction manual for the hard disk and describes how to install the hard disk into a computer.

During its operation, the drive practically does not heat up. Seagate hard drives are traditionally moderately priced. In short, if you are accustomed to leisurely work on your computer and reliability is the most important factor for you when buying, then buy a Seagate hard drive

Western Digital 450 АА

Western Digital is quite persistent and successful in competing with Fujitsu and IBM. WD solutions have always been renowned for their good speed characteristics. There were times when the company managed (albeit for a short period of time) to become the leaders in the IDE segment. V this moment Western Digital solutions are in no way inferior to all their competitors.

I will give the technical characteristics of the model in question:

Western Digital 450AA
Device volume 45 GB
RPM speed 5.400 revolutions per second
Average access time 9.5 ms
Built-in cache size 2048 Kb
Factory warranty 3 years

The model has a good capacity, but the speed of working with data leaves much to be desired. Of course, on average, this model, despite the lower number of disk revolutions than the previous models, will outperform its counterparts from Seagate and Samsung, but it will not be enough for more. The model is loud enough. When working with defragmented data, the sounds of head positioning are clearly audible even among the powerful Golden Orb. The temperature of the hard drive with frequent use rises to a level that does not require additional cooling.

I cannot but note the company's bad habit of "forgetting" to put information about the position of the jumpers on the hard drive. You often have to visit the company's website to get this data. The required positions are marked in the figure.

Among the pluses, I can note a fairly decent reliability, although there is no "batch for batch". The cost of the model is similar to that of competitors from Fujitsu. I recommend buying this model to users whose interests lie in the field of business. Office applications run fast enough on this hard drive, and its reliability guarantees their safety.

Conclusion

As a result, I want to offer you a table that clearly shows which disk you need to purchase to solve certain problems.

Hard disk name IBM DTLA 307045 Fujitsu MPF-3204AH Seagate Barracuda ATA ST320430A Western Digital 450 АА
Main characteristics (size, revolutions, cache, average access time) > 45 GB 7200 rps 2048 KB 8.5 ms > 20.4 GB 7200 rps 2048 KB 8.5 ms > 20.4 GB 7200 rps 512Kb 7.6 ms > 45 GB 5400 RPM 2048 KB 9.5 ms
Warranty obligations 3 years 3 years 3 years 3 years
Main characteristics Pros: highest speed Cons: low reliability, high temperature, high price Pros: Good speed characteristics, good reliability, absolute noiselessness Cons: poor prevalence Pros: Very high reliability, low cost Cons: low speed characteristics Pros: Good speed performance Cons: Overpriced

Unfortunately, at the moment I can not present the results of testing two more hard drives. You probably already guessed, these are Samsung and Maxtor. In our next article we will talk about these hard drives and, in addition, we will tell you about the basic methods of testing hard drives.

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

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

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

Figure: Hard drive without top cover

The note!

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

How a hard drive works

Recording and reading of information located on concentric circles of the hard disk, divided into sectors, is performed by means of universal read / write heads.

All sides of the disc provide their own track for writing and reading, however, the heads are located on a drive common to all discs. For this reason, the heads move synchronously.

YouTube Video: Open Hard Drive Working

Normal operation of the drive does not allow touching between the heads and the magnetic surface of the disk. However, in the event of a power outage and the device stops, the heads still fall onto the magnetic surface.

During work hard a small air gap is formed between the surface of the rotating plate and the head. If a speck of dust enters this gap or the device is shaken, there is a high probability that the head will collide with the rotating surface. Severe impact may damage the head. The result of this output can be damage to several bytes or complete inoperability of the device. For this reason, in many devices, the magnetic surface is alloyed, after which a special lubricant is applied to it, which makes it possible to cope with the periodic shaking of the heads.

Some modern discs use a loading / unloading mechanism that prevents the heads from touching the magnetic surface even in the event of a power outage.

High and low level formatting

Using high-level formatting allows the operating system to create structures that make it easier to work with files and data stored on the hard disk. All existing partitions (logical drives) are provided with a volume boot sector, two copies of the file allocation table and a root directory. Through the above structures, the operating system manages to allocate disk space, track the location of files, and bypass damaged areas on the disk.

In other words, high-level formatting boils down to creating table of contents for the disk and file system (FAT, NTFS, etc.). Only formatting can be referred to as "real" formatting low level, during which the disk is divided into tracks and sectors. By means of the DOS FORMAT command, a floppy disk undergoes both types of formatting at once, while a hard disk only undergoes high-level formatting.

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

Organization of several partitions provides the ability to install on each of them its own operating infrastructure with a separate volume and logical drives. Each volume or logical drive has its own letter designation (for example, drive C, D or E).

What does a hard drive consist of?

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

disks(their number most often reaches 5 pieces);

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

actuator mechanism(this mechanism sets the heads to the required position);

disc drive motor(device that drives discs in rotation);

air filter(filters located inside the drive housing);

printed circuit board with control schemes(through this component, the drive and the controller are controlled);

cables and connectors(electronic components HDD).

A sealed box - HDA is most often used as a housing for discs, heads, a head drive mechanism and a disc drive motor. Typically, this box is a single unit that is almost never opened. Other non-HDA components such as configuration items, printed circuit board, and bezel are removable.

Automatic head parking and monitoring system

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

During constant ups and downs, the inevitable abrasion of the magnetic layer occurs. If, after wear and tear, the drive is shaken, it is likely that the disk or heads will be damaged. To prevent the above troubles, modern drives are equipped with a special loading / unloading mechanism, which is a plate that is placed on the outer surface of hard drives. This measure prevents touching the head and the magnetic surface even if the power is turned off. When the voltage is disconnected, the drive independently "parks" the heads on the surface of the inclined plate.

A little about air filters and air

Almost all hard drives are equipped with two air filters: a barometric air filter and a recirculation filter. The difference between the above filters from the replaceable models used in older generation drives is that they are placed inside the case and their replacement is not provided until the end of the service life.

Older discs used the technology of constant distillation of air inside the case and back, using a filter that needed periodic replacement.

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

Interface connectors and connections

Many modern hard disk drives have multiple interface connectors for connecting to a power source and to the system as a whole. Typically, a drive contains at least three types of connectors:

interface connectors;

connector for power supply;

grounding connector.

Interface connectors deserve special attention, since they are intended for receiving / transmitting commands and data by the drive. Many standards do not exclude the possibility of connecting multiple drives to one bus.

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

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

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

Serial ATA- a connector that replaces IDE, which is physically a unidirectional line used for serial data transmission. While in compatibility mode, the interface is similar to the IDE, however, the presence of the "native" mode allows you to take advantage of an additional set of features.

SCSI- a universal interface that was actively used on servers to connect HDD and other kinds of devices. Despite good technical performance, it did not become as common as IDE due to its high cost.

SAS- serial analogue of SCSI.

USB- an interface that is required to connect external hard drives. In this case, the exchange of information occurs via the USB Mass Storage protocol.

Firewire- a connector similar to USB, required to connect an external HDD.

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

Quality indicators of hard drives

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

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

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

Physical capacity limitations

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

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

BIOS versions also reduced the maximum hard drive capacity, so systems built before 1998 had capacities up to 8.4 GB, and systems built before 1994 had 528 MB.

Even after solving the problems with the BIOS, the limitation of the capacity of drives with the ATA connection interface remained, its maximum value was 137 GB. This limitation was overcome by the ATA-6 standard released in 2001. This standard used an extended addressing scheme, which, in turn, contributed to the increase in storage capacity up to 144 GB. Such a solution made it possible to show the world drives with PATA and SATA interfaces, in which the amount of information that can be stored is higher than the specified limit of 137 GB.

OS limits on maximum volume

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

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

There is also a hard disk capacity limitation if Windows 95 is installed. The maximum value for this limitation is 32 GB. In addition, updated versions of Windows 95 are supported only by file system FAT16, which in turn imposes a 2GB limit on partition sizes. It follows from this that in the case of using a 30 GB hard disk, it must be divided into 15 partitions.

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

Characteristics and parameters

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

The first thing to look at is the type of interface used. Recently, every computer has begun to use SATA.

The second no less important point is the amount of free space on the hard disk. Its minimum value today is only 80 GB, while the maximum is 4 TB.

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

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

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

Hard disk speed

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

Spindle speed, which is measured in revolutions per minute. Its task is not to directly identify the real exchange rate, it only allows you to distinguish a faster device from a slower device.

Access time... This parameter calculates the time taken by the hard drive from receiving a command to transmitting information over the interface. Most often, the average and maximum values ​​appear.

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

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

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

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

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

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

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

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

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

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

Reliability factor

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

Cost and price

Every day the cost of HDD is getting lower. So, for example, today the price of a 500 GB ATA hard drive is on average $ 120, compared to $ 1,800 in 1983 for a 10 MB hard drive.

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

Decoding of marking of internal WD hard drives:

(1) WD (2) 000 (3) 0 (4) A (5) B (6) C (7) D

1 ... Western Digital.

2 ... One or three digits are used to determine the volume of the disc. The volume is measured in the values ​​specified in clause 4.

3 ... 0 - serves to highlight some features. For example, the WD5001ABYS disk differs from the WD5000ABYS only in that the former has a perpendicular recording method versus the parallel one in the latter.

4 ... The letter describing the value in which the volume specified in clause 2 is measured, and the form factor of the disk:

  • A - gigabyte / 3.5 ",
  • B - gigabyte / 3.5 "or gigabyte / 2.5",
  • C - 3.5 ",
  • E - terabyte / 3.5 ",
  • F - 10 gigabytes / 3.5 ",
  • G / H - gigabyte / 3.5 ",

5 ... A letter that describes the market segment for which the disc is intended and the family to which it belongs:

  • A - Desktop / Caviar;
  • B - Enterprise / RE2 (3-platter) / RE2-GP;
  • D - Enterprise / Raptor;
  • E, P - Mobile / Scorpio Blue
  • G - Enthusiast / Raptor X;
  • J - Mobile / Scorpio Black
  • L - Enterprise / VelociRaptor;
  • V - Audio-Video (Audio and Video Equipment);
  • Y - Enterprise / RE2 (4-platter) / RE2-GP / RE3 / RE4.

6 ... A letter describing the rpm and cache size:

  • B - 7200 rpm and 2 MB cache;
  • C - Caviar Green and 16 MB cache;
  • D - Caviar Green and 32 MB cache;
  • F - 10000 rpm and 16 MB cache;
  • G - 10000 rpm and 8 MB cache;
  • H - 10000 rpm and 32 MB cache;
  • J - 7200 rpm and 8 MB cache;
  • K - 7200 rpm and 16 MB cache;
  • L - 7200 rpm and 32 MB cache;
  • P - RE2-GP and 16MB cache;
  • Y - RE2 / RE3 and 16 MB cache or RE4 and 64 MB cache;
  • R - Caviar Green, 64MB cache and Advanced Format;
  • S / E - 7200 rpm and 64 MB cache V - 5400 rpm and 8 MB

7 ... The letter describing the hard disk interface:

  • B - PATA-100;
  • E - PATA-133;
  • D - SATA-150;
  • S - SATA-300;
  • X - SATA-600.

Old markings

The above is relative new way marking. Previously, a template was used in which pp. 4-5 were absent; two or three digits were allocated for the disk size (the volume was measured in gigabytes); the next digit was reserved for all families; in clause 6, the letter L (7200 rpm / 2 MB) was also used, and the letter P had a different meaning - 7200 rpm / 8 MB; in clause 7, the letter R (SATA-150) was also used.

For example: WD800JB: 80 GB, 8 MB buffer, 7200 rpm, IDE, and WD800JD: 80 GB, 8 MB buffer, 7200 rpm, SATA; WD5000AAKS: 500 GB, 3.5 "Caviar Family, 16 MB, 7200 rpm, SATA2; WD5000BEVT: 500 GB, 2.5", 8 MB, 5400 rpm, SATA2.

Note:

  1. WD10EADS-00P8B0 and WD15EADS-00P8B0 drives can have severe visible slowdowns at random times in the write / read processes, which are difficult to diagnose / catch when calling under warranty.
  2. WDxxEARS drives have an Advanced Format, which imposes special features on their operation.

FAQ

1. I heard that WD hard drives have a ramp. What is it for?

Indeed, some WD drives have a ramp. It contains the head block when the pancakes are spinning, stop, or when the drive is turned off. This contributes to an increase in the shock resistance of the drive when inoperative, and in the long term, the reliability of operation increases due to a decrease in contact and wear of the plates and heads.

2. In what mode are SATA-300 drives supplied?

Hard drives with the index “S” (SATA-300) are sold with SATA-300 enabled and Spread Spectrum Clocking (SSC) disabled.

3. What are jumpers used for?

Contact closure 1-2 leads to the inclusion of the Spread Spectrum Clocking function.
Contact closure 3-4 will enable Power Management mode (PM2 enable mode: to enable power supply in standby mode, place a jumper on pins 3-4. This mode will provide controlled unwinding using the unwind command in accordance with the ATA standard and is intended mainly for server operation / workstations operating in multi-disk configurations.
Important! PM2 mode requires a compatible BIOS that supports this function. If PM2 is enabled and is not supported by the BIOS, the hard disk will not spin up and therefore will not be detected by the system.
Note: The PM2 feature does not work on all WD SATA drives).
Closing contacts 5-6 will enable SATA150 transfer mode.
Contact closure 7-8 will cause one sector shift of partitions in Advanced Format disks.

4. Some WD drives have two power connectors: SATA and Molex. Which one should I connect to?

You can connect power to either, but not both at the same time.

5. All the hard drives that I have seen have a board with electronics on the bottom. I bought WD, so this board is empty for him! This is fine?

For WD hard drives, the electronics board is inverted. This technique, according to WD, allows you to solve two problems at once - to protect microcircuits from external influences and to ensure their cooling. Since the microcircuits are under a layer of PCB, it is impossible to accidentally damage them with a sharp object when unpacking and installing the hard drive in the case. They are also protected from static electricity. There is a layer of thermally conductive material between the PCB and the case, thanks to which the microcircuits can give off heat to the metal.

6. Why are acceleration sensors installed on WD electronics boards?

There are one or two acceleration sensors on the boards that are used to detect vibration of the drive during operation and allow the controller to compensate for the movement / acceleration of the actuator caused by these vibrations. They allow you to quickly and accurately get on the desired track even in conditions of increased vibration (RAFF technology - p.17g).

7. What warranty does WD provide for its desktop hard drives?

3 years on the Caviar Green / Blue series and 5 years on the Caviar Black, RE and Raptor series.

8. What are the differences between the Caviar Green, Caviar Blue, Caviar Black series?

Green - slow, quiet, cold, low consuming disks. The spindle rotation speed is in the range of 5000-5600 rpm (ie the speed is fixed, but it can be different for different models). Great for storing data. Park in idle time (have a ramp). The parking function can interfere with the user, then you need to disable it using the wdidle utility.
Blue - regular wheels general purpose... Spindle rotation speed - 7200 rpm.
Black - positioned as high-performance discs. Differences from Blue: have a dual-core processor (marketing says “two processors”); may have more cache than Blue- "classmate"; air spoiler plates that cut the air currents; double spindle mount (on the bottom on the platform with the motor and on the top on the cover); double actuator on some models; 5 years warranty.

9. What are the differences between the Raptor series drives and the Caviar Blue / Black drives?

The main difference is the rotation speed of the Raptor at 10,000 rpm versus 7200 at the Caviar. As a consequence, the Raptor's access times are significantly shorter. Raptor discs come with a 5-year warranty.

The Raptor X is a regular Raptor with a large clear lens on the top, through which you can watch it work.

In addition, VelociRaptor discs have 2.5 "platters and 2.5" format, which further reduces access time.
Some VelociRaptor models (WD3000GLFS and WD3000HLFS) can be installed in both 2.5 "and 3.5" bays. For this, a metal heatsink of 3.5 "format supplied with the disc is used, which, together with the drive fixed in it, is screwed in with standard screws in the 3.5" compartment.

10. What are the differences between Caviar RE series and Caviar Green / Blue / Black?

RE stands for "RAID Edition". RE series disks have increased MTBF, different firmware, support TLER technology (see p. 17c). The manufacturer is positioned for professional applications, for example, in storage systems or servers / workstations when working in RAID arrays. They are guaranteed for 5 years.
They have two processors; vibration compensation system; head flight adjustment system; TLER system; ramp.
The RE-GP Series are the Green Series discs with RE Series features.

11. What is the difference between WD5000AAKS and WD5000KS drives?

Their main difference (and this applies to all models, the marking of which is distinguished only by the presence of "AA" in one and the absence of the other) is that a disc with "AA" has a significantly higher recording density than a disc without it. Such drives have fewer platters, which means they are faster, consume a little less power and have a slightly lower temperature (for example, the WD5000KS contains four pancakes, and the WD5000AAKS - three). Naturally, disks with "AA" are newer.

12. Should you buy a RE hard drive for your home system?

Note that, in my opinion, the above features of this series at home practically do not give any advantages. Now let's look at the strategy for the behavior of different disks on different systems.
Ordinary desktop disks are designed to work independently, and when connected to a RAID controller, they are not even aware of its presence. If errors occur during the operation of the drive, then its firmware tries to correct them on its own using the built-in error correction system. If the repair process takes more than 8 seconds (although there is no standard for controller latency, these 8 seconds are typical for most RAID controllers), then the RAID controller considers the disk to be faulty and disconnects it from the array, which can lead to unpleasant consequences.
For a WD hard drive using TLER technology (p. 18c), the situation is different. If an error occurs, the drive tries to fix it on its own for 7 seconds, and then transfers information about the error to the RAID controller, which decides whether to fix it now or leave it for later.
However, if the opposite situation arises (the hard drive with TLER works outside the RAID), the drive "thinks" that it is connected to the RAID controller, and if it is impossible to correct the error by its own means, it admits its powerlessness and suggests that the controller should solve the problem. And he is not ...
Therefore, Western Digital itself does not recommend installing a WD hard drive with TLER in a system where RAID is not planned.

13. What is the maximum temperature for WD hard drives?

For modern WD hard drives, the maximum permissible temperature is 60 degrees on the surface of the can. However, this does not mean that the drive will be able to work for a long time with such heating.

14. All programs show that my WD hard drive has a temperature of 70 degrees. What to do?

According to Western Digital technical support, hard drives released from October 25, 2005 to mid-April 2006 had problems with the calibration of the thermal sensor, and therefore it shows a temperature higher than the real one by 20 or more degrees. The problem is treated by changing the firmware.

15. Does WD have perpendicular discs?

This recording method is used in the WD7500AAKS and all newer models in all series.

16. Is it true that the spindle speed of Caviar Green hard drives varies from 5400 to 7200 rpm depending on the load?

No, this is just a marketing ploy by the manufacturer. In fact, the situation is as follows: for the Caviar Green WD family, the possibility of different spindle speeds on different models, but on each specific drive, this speed is CONSTANT, as evidenced by a quote from the description of IntelliPower technology: "For each GreenPower drive model, WD may use a different, invariable RPM" (http://www.westerndigital.com/en/library/sata / 28).
Because WD does not disclose what the true speed of the released models is, hiding behind the meaningless IntelliPower label, you have to rely on the test results. So, according to various tests, the assumption is confirmed that all Caviar Green hard drives now have 5400 (much more often) and 5000 (less often) rpm (for example, http://www.storagereview.com/1000.sr?page=0 % 2C2, http://www.silentpcreview.com/article786-page2.html). Thus, the current "green" WD drives have a speed of 5400 or 5000 rpm, which DOES NOT CHANGE during operation.

17. Where is the temperature sensor located on the WD drives?

Inside the jar in the area marked with a red circle. It is the temperature of this sensor that is displayed in the S.M.A.R.T.

18. What proprietary technologies does WD have?

a) SecureConnect - more reliable connection SATA connectors(requires a special cable from WD);
b) FlexPower - availability of both SATA and molex power connectors;
c) TLER (RAID-specific Time-Limited Error Recovery) - allows you to reduce the time required to recover read errors, reduces the percentage of RAID failure (see clause 13);
d) RAFF (Rotary Accelerator Fead Forward) - optimizes disk performance when operating in vibration conditions such as rack servers and NAS.
e) SoftSeek - reduces the noise of the actuator during positioning, optimizing the shape of the control signal supplied to the actuator when moving them over long distances;
f) IntelliPark - parking heads in idle mode (used in Caviar Green);
g) IntelliSeek - approaching the head unit to the desired sector just at the moment it comes under the head, instead of a frantic flight to the track and further waiting for the desired sector.

19. How to use the wdidle program to change the parking parameters of hard drives when idle?

wdidle should be copied to a bootable DOS CD / DVD / flash drive, put the SATA controller in IDE mode, disconnect other drives just in case, boot from bootable media... Then run the program with the appropriate parameters:
/ S - sets a timer for the time after which the disk parks the heads in the absence of calls to it, in hundreds of milliseconds (the parameter can be from 1 to 255). By default, it is 80, i.e. 80 * 100 ms = 8000 ms = 8 s;
/ D - prohibits parking;
/ R - displays the current value of the timer;
/? - displays the help utility.

20. What is technologyAdvanced Format?

This is a technology used in the production of some series of new terabyte HDDs. Its essence lies in the fact that the surface of the disks is divided into sectors of non-standard size - 4 KB versus 512 bytes ordinary. This works well for working with files. big size and vice versa, it is negative when working with small files. Thus, it is better to use such HDDs only for creating file storages, but not for active work with the disk, otherwise it threatens to decrease performance.

In addition, for such disks to work with Windows XP, their formatting is possible only special utility WD Align, otherwise you will again notice a catastrophic decrease in performance.

21. How can I find out the number of platters and heads in different WD hard drives? There is nothing in the specs.

WD is often accused of not providing information on the number of heads and platters in specific drives. end user... Therefore, you have to extract this information from reviews. Here's what we managed to find out:

a) disks up to 160 GB:

  • WD400Bx - 1 plate / 1 head;
  • WD800xx - ½;
  • WD1200xx - 2/3;
  • WD1200AAxx - ½;
  • WD1600xx - 2/4;
  • WD1600AAxS (B) - ½;

b) disks with a volume of 250-400 GB:

  • WD2500xx - 3/6;
  • WD2500AAxS (B) - 2/4, with "B3A", "B4A", "VSA" or "VTA" in the model number (MDL) - ½;
  • WD2500AAKX -? / ?;
  • WD2502ABYS - ½;
  • WD2503ABYX - 1/1;
  • WD3000xx - 3/6;
  • WD3200xx - 3/6;
  • WD3200AAxS (B) - 2/4, with "B3A" or "B4A" - ½;
  • WD3200AAKX -? / ?;
  • WD3200AALX -? / ?;
  • WD3202ABYS - ½;
  • WD4000xx - 4/8;
  • WD4000AAxS (B) - 3/5;

v) 500 GB disks:

  • WD5000KS - 4/8;
  • WD5000AAxS (B) - 3/6, with "A7B", "A8B" or "L9A" - 2/4, with "M9A" or "V1A" - ½;
  • WD5000AAKX -? / ?;
  • WD5000AALX -? / ?;
  • WD5001AALS - 2/4;
  • WD5002AALX -? / ?;
  • WD5000AACS - 2/4 and 2/3;
  • WD5000AADS - ½;
  • WD5000ABPS - 2/4;
  • WD5000YS - 4/8;
  • WD5000ABYS - 3/6;
  • WD5002ABYS - 2/4;
  • WD5003ABYX - ½;

G) disks with a volume of 600-800 GB:

  • WD6000HLHX - 3 / ?;
  • WD6400AAKS - 2/4, with "H2B" - 2/3;
  • WD6401AALS - 2/4;
  • WD6400AALX -? / ?;
  • WD6402AAEX - 2/3;
  • WD6400AACS - 2/4;
  • WD6400AADS - 2/3;
  • WD6400AARS - 2/3;
  • WD7500AAKS - 4/8;
  • WD7501AALS - 3/5;
  • WD7500AALX -? / ?;
  • WD7502AAEX -? / ?;
  • WD7500AACS - 3/6, with "DB6" - 3/5;
  • WD7500AADS - 2/3;
  • WD7500AYPS - 3/6;
  • WD7502ABYS - 3/5;
  • WD8000AARS - 2/3;

e) 1-1.5 TB disks:

  • WD1001FALS - 3/6, with "E3A" or "U9B" - 2/4;
  • WD1002FAEX - 2/4;
  • WD10EALS - 2/4;
  • WD10EALX -? / ?;
  • WD10EACS - 4/8, with "D6B" - 3/6;
  • WD10EADS - 3/6, with "M2B" - 2/4, with "P8B" - 2/4, 5000 rpm;
  • WD10EARS - 2/4, with "Z5B" - 5000 rpm;
  • WD1000FYPS - 4/8;
  • WD1002FBYS - 3/6;
  • WD1003FBYX - 2/4;
  • WD15EADS - 3/6 and 4/7;
  • WD15EARS - 3/6;
  • WD1501FASS -3/6;
  • WD1502FAEX -? / ?;
  • WD1502FYPS - 3/6;
  • WD1503FYYS - 3/6;

e) disks with a volume of 2 TB and higher:

  • WD20EADS - 4/8;
  • WD20EARS - 4/8, with "MVWB" - 3/6;
  • WD2002FYPS - 4/8;
  • WD2001FASS - 4/8;
  • WD2002FAEX -? / ?;
  • WD2003FYYS - 4/8;
  • WD25EZRS -? / ?;
  • WD30EZRS - 4/8.

How does a hard drive work? What kind of hard drives are there? What role do they play in the computer? How do they interact with other components? What parameters to consider when choosing and buying a hard drive, you will learn from this article.

HDD- abbreviated name from " Hard Drive Magnetic Disks ". Also you will come across English HDD- and slang Winchester or abbreviated Screw.

In a computer, the hard drive is responsible for storing data. Operating room Windows system, programs, films, photos, documents, all information that you download to your computer is stored on your hard drive. And the information in the computer is the most valuable thing! If a processor or video card is out of order, you can buy and replace them. Lost family photos from last summer's vacation or a year's accounts of a small business, on the other hand, are not easy to recover. Therefore, special attention is paid to the reliability of data storage.

Why is a rectangular metal box called a disc? 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 Discovery Channel show about how the hard drive works and works.

Three more things you need to know about hard drives.

  1. The hard drive is the slowest part of the computer. When the computer freezes, look at the hard drive activity indicator. If it blinks frequently or is on continuously, then the hard drive is executing commands from one of the programs and all the rest are idle, waiting for their turn. If the operating system does not have enough fast RAM to run a program, it uses up hard disk space, which dramatically slows down the entire computer. Therefore, one of the ways to increase the speed of your computer is to increase the size of the RAM.
  2. 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 "hover" over the disc in the air flow created by the rotating disc. The distance between the disc and the heads in modern devices is about 10 nm. If the disc is bumped or jolted at this point, the head may touch the disc and damage the data surface. As a result, the so-called " badblocks"- unreadable areas, because of which the computer cannot read any file or boot the system. In the off state, the heads are" parked "outside the working area and overloads from impact are not so terrible for the hard disk. Please make backups of important data !
  3. The hard drive capacity is often slightly less than what the vendor or manufacturer indicates. The reason is that manufacturers indicate the size of a disk based on the fact that there are 1,000,000,000 bytes in one gigabyte, while there are 1,073,741,824.

We buy a hard drive

If you decide to increase the volume of information storage in your computer by connecting extra hard disk or replacing the old one with a more capacious one, what do you need to know when buying?

First, look under the cover of your computer's system unit. You need to find out which interface connect hard the disk is supported by the motherboard. Today, the most common standards SATA and moribund IDE... They are easy to distinguish by their appearance. The picture on the left shows a fragment of the motherboard, which is equipped with connectors of both types, 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 a speed 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, as a result the data transfer rate will be limited to the slower version. In this case, the speed of the hard disk is even slower. Therefore, the potential of fast interfaces will be able to unfold only with the advent of new high-speed storage devices.

If you decide to purchase an additional hard SATA drive, check if you have interface cable like on a picture. It is not sold with the disc. (Usually they come with the motherboard.) Also, among the power supply connectors there must be at least one free one 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, keep in mind that it will turn out to 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, you can determine empirically. Large volumes may be required, for example, to record high quality video. Modern HD movies reach several tens of Gigabytes.

In addition, among the main parameters indicate:

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

Greetings to all blog readers. Many people are interested in the question of how a computer's hard drive works. Therefore, I decided to devote today's article to this.

A computer hard disk (HDD or hard drive) is needed to store information after the computer is turned off, in contrast to RAM () - which stores information until the power supply is cut off (before the computer is turned off).

A hard drive can rightfully be called a real work of art, only an engineering one. Yes Yes exactly. Everything is so complicated inside there. At the moment, all over the world, a hard disk is the most popular device for storing information; it is on a par with such devices as: flash memory (flash drives), SSD. Many have heard a lot about the complexity of a hard disk device and are perplexed as to how so much information can fit in it, and therefore would like to know how a computer's hard disk works or what it consists of. Today there will be such an opportunity).

A hard drive has five main parts. And the first one is integrated circuit , which synchronizes the work of the disk with the computer and controls all processes.

The second part is an electric motor(spindle), causes the disc to rotate at approximately 7200 rpm, and the IC keeps the rotational speed constant.

And now the third, probably the most important part is the rocker arm, which can both write and read information. The end of the rocker arm is usually split to handle multiple discs at once. However, the rocker head never makes contact with the discs. There is a gap between the surface of the disc and the head, the size of this gap is about five thousand times less than the thickness of a human hair!

But let's still see what happens if the gap disappears and the rocker head comes into contact with the surface of the rotating disc. We still remember from school that F = m * a (Newton's second law, in my opinion), from which it follows that an object with a small mass and a huge acceleration becomes incredibly heavy. Considering the enormous rotational speed of the disc itself, the weight of the rocker head becomes very, very noticeable. Naturally, damage to the disc is inevitable in this case. By the way, here's what happened to the disk, in which this gap disappeared for some reason:

The role of the friction force is also important, i.e. its almost complete absence, when the rocker begins to read information, while shifting up to 60 times per second. But wait, where is the engine here that sets the rocker in motion, and even at such a speed? In fact, it is not visible, because it is an electromagnetic system operating on the interaction of 2 forces of nature: electricity and magnetism. This interaction allows you to accelerate the rocker to the speed of light, in the literal sense.

Fourth part- the hard disk itself is where the information is written and from where the information is read, by the way, there may be several of them.

Well, the fifth and final part of the hard drive design is, of course, the case in which all the other components are installed. The materials used are as follows: almost the entire body is made of plastic, but the top cover is always metal. The assembled case is often called a "containment". There is an opinion that there is no air inside the containment zone, or rather, that there is a vacuum. This opinion is based on the fact that at such high speeds of rotation of the disk, even a speck of dust that gets inside can do a lot of bad things. And this is almost true, except that there is no vacuum there - but there is purified, dried air or neutral gas - nitrogen, for example. Although, perhaps in earlier versions of hard drives, instead of purifying the air, it was simply pumped out.

We talked about components, i.e. what does a hard drive consist of... Now let's talk about data storage.

How and in what form is data stored on a computer hard drive

Data is stored in narrow lanes on the surface of the disc. During production, more than 200 thousand of such tracks are applied to the disc. Each of the tracks is divided into sectors.

Track and sector maps allow you to determine where to write or read information. Again, all the information about the sectors and tracks is in the memory of the integrated circuit, which, unlike other components of the hard drive, is not located inside the case, but outside and usually at the bottom.

The surface of the disc itself is smooth and shiny, but this is only at first glance. On closer inspection, the surface structure is more complex. The fact is that the disc is made of a metal alloy coated with a ferromagnetic layer. This layer does all the work. The ferromagnetic layer remembers all the information, how? Very simple. The rocker head magnetizes a microscopic area on the film (ferromagnetic layer), setting the magnetic moment of such a cell in one of the states: o or 1. Each such zero and one are called bits. Thus, any information recorded on a hard disk is in fact a certain sequence and a certain number of zeros and ones. For example, a good quality photo takes up about 29 million of these cells, and is scattered across 12 different sectors. Yes, it sounds impressive, but in reality - such a huge number of bits occupies a very small area on the surface of the disc. Every square centimeter of hard disk surface contains tens of billions of bits.

How a hard drive works

We have just examined the device of the hard drive, each of its components separately. Now I propose to link everything into a kind of system, due to which the principle of the hard disk operation will be clear.

So, the principle by which a hard drive works next: when the hard disk is turned on, it means that either it is being written to it, or information is being read from it, or from it, the electric motor (spindle) starts to gain momentum, and since the hard disks are fixed on the spindle itself, respectively, they are together with it also start to rotate. And until the revolutions of the disc (s) have reached such a level that an air cushion is formed between the rocker arm and the disc, the rocker is in a special "parking zone" to avoid damage. This is what it looks like.

As soon as the revolutions reach the desired level, the servo drive (electromagnetic motor) sets the rocker in motion, which is already positioned in the place where you need to write or read information from. This is facilitated by the integrated microcircuit, which controls all the movements of the rocker arm.

There is a widespread opinion, a kind of myth, that at the moments of time when the disk is "idle", i.e. temporarily no read / write operations are performed with it, the hard disks inside stop spinning. This is really a myth, because in fact, the hard drives inside the case rotate constantly, even when the hard drive is in power-saving mode and nothing is written to it.

Well, here we have examined with you the device of the computer hard disk in all details. Of course, within the framework of one article, it is impossible to tell about everything related to hard drives. For example, this article did not say about it - this is a big topic, I decided to write a separate article about it.

Found interesting video, about how the hard drive works in different modes

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