Hard drives, or, as they are also called, hard drives, are one of the most important components computer system. Everyone knows about it. But far from every modern user even in principle guesses how a hard drive functions. The principle of operation, in general, is quite simple for a basic understanding, but there are some nuances, which will be discussed further.
Questions about the purpose and classification of hard drives?
The question of purpose is, of course, rhetorical. Any user, even the most entry-level, will immediately answer that the hard drive (aka hard drive, aka Hard Drive or HDD) will immediately answer that it is used to store information.
In general, it is true. Do not forget that on the hard disk, in addition to the operating system and user files, there are boot sectors created by the OS, thanks to which it starts, as well as some marks by which you can quickly find the necessary information on the disk.
Modern models are quite diverse: conventional HDDs, external hard drives, high-speed solid-state SSD drives, although it is not customary to attribute them to hard drives. Next, it is proposed to consider the device and the principle of operation hard drive, if not in full, then at least in such a way that it is enough to understand the basic terms and processes.
Please note that there is also a special classification of modern HDDs according to some basic criteria, among which the following can be distinguished:
- method of storing information;
- media type;
- way of organizing access to information.
Why is a hard drive called a hard drive?
Today, many users are thinking about why they call hard drives related to small arms. It would seem that what can be common between these two devices?
The term itself appeared back in 1973, when the world's first HDD appeared on the market, the design of which consisted of two separate compartments in one sealed container. The capacity of each compartment was 30 MB, which is why the engineers gave the disk the code name "30-30", which was fully consonant with the brand of the popular at that time gun "30-30 Winchester". True, in the early 90s in America and Europe this name practically fell into disuse, but it still remains popular in the post-Soviet space.
The device and principle of operation of the hard drive
But we digress. The principle of operation of a hard disk can be briefly described as the processes of reading or writing information. But how does it happen? In order to understand the principle of operation of a magnetic hard drive, it is first necessary to study how it works.
The hard drive itself is a set of platters, the number of which can vary from four to nine, interconnected by a shaft (axis) called a spindle. The plates are placed one above the other. Most often, the material for their manufacture is aluminum, brass, ceramics, glass, etc. The plates themselves have a special magnetic coating in the form of a material called platter, based on gamma ferrite oxide, chromium oxide, barium ferrite, etc. Each such plate is about 2 mm thick.
Radial heads are responsible for writing and reading information (one for each plate), and both surfaces are used in the plates. For which it can range from 3600 to 7200 rpm, and two electric motors are responsible for moving the heads.
At the same time, the basic principle of the computer hard drive is that information is not recorded anywhere, but in strictly defined locations, called sectors, which are located on concentric tracks or tracks. To avoid confusion, uniform rules apply. This means that the principles of operation of hard disk drives, from the point of view of their logical structure, are universal. So, for example, the size of one sector, adopted as a single standard throughout the world, is 512 bytes. In turn, sectors are divided into clusters, which are sequences of adjacent sectors. And the features of the principle of operation of a hard disk in this regard are that the exchange of information is carried out by whole clusters (an integer number of chains of sectors).
But how is information read? The principles of operation of a hard disk drive are as follows: using a special bracket, the reading head moves in a radial (spiral) direction to the desired track and, when rotated, is positioned above a given sector, and all heads can move simultaneously, reading the same information not only from different tracks , but also from different disks (platters). All tracks with the same serial numbers are called cylinders.
At the same time, one more principle of hard disk operation can be distinguished: the closer the read head is to the magnetic surface (but does not touch it), the higher the recording density.
How is information written and read?
Hard drives, or hard drives, were called magnetic because they use the laws of physics of magnetism, formulated by Faraday and Maxwell.
As already mentioned, plates made of non-magnetically sensitive material are coated with a magnetic coating, the thickness of which is only a few micrometers. In the process of work, a magnetic field arises, which has the so-called domain structure.
The magnetic domain is a magnetized region of a ferroalloy strictly limited by boundaries. Further, the principle of operation of a hard disk can be briefly described as follows: when an external magnetic field, the disk's own field begins to orient itself strictly along the magnetic lines, and when the impact stops, zones of residual magnetization appear on the disks, in which the information that was previously contained in the main field is stored.
The reading head is responsible for creating an external field during recording, and when reading, the residual magnetization zone, being opposite the head, creates an electromotive force or EMF. Further, everything is simple: the change in the EMF corresponds to unity in binary code, and its absence or termination is zero. The time of change of the EMF is usually called a bit element.
In addition, the magnetic surface, purely for computer science reasons, can be associated as a certain dotted sequence of bits of information. But, since the location of such points cannot be absolutely accurately calculated, it is necessary to set some pre-provided marks on the disk that helped determine the desired location. The creation of such marks is called formatting (roughly speaking, breaking the disk into tracks and sectors combined into clusters).
The logical structure and principle of operation of the hard disk in terms of formatting
As for the logical organization of the HDD, formatting comes first here, in which two main types are distinguished: low-level (physical) and high-level (logical). Without these steps, there is no need to talk about bringing the hard drive into working condition. How to initialize a new hard drive will be discussed separately.
Low-level formatting involves a physical impact on the surface of the HDD, which creates sectors located along the tracks. It is curious that the principle of operation of a hard disk is such that each created sector has its own unique address, which includes the number of the sector itself, the number of the track on which it is located, and the number of the side of the plate. Thus, when organizing direct access, the same RAM accesses directly to a given address, and does not search for the necessary information over the entire surface, due to which speed is achieved (although this is not the most important thing). Please note that when performing low-level formatting, absolutely all information is erased, and in most cases it cannot be restored.
Another thing is logical formatting (on Windows systems, this quick format or Quick format). In addition, these processes are applicable to the creation of logical partitions, which are some area of the main hard drive that works according to the same principles.
Logical formatting primarily affects the system area, which consists of the boot sector and partition tables (boot record boot record), file allocation table (FAT, NTFS, etc.) and the root directory (Root Directory).
Information is written to sectors through the cluster in several parts, and one cluster cannot contain two identical objects (files). Actually, the creation of a logical partition, as it were, separates it from the main system partition, as a result of which the information stored on it, when errors and failures occur, is not subject to change or deletion.
HDD Main Features
It seems that in general terms the principle of the hard drive is a little clear. Now let's move on to the main characteristics, which give a complete picture of all the possibilities (or disadvantages) of modern hard drives.
The principle of operation of the hard drive and the main characteristics can be completely different. To understand what we are talking about, let's highlight the most basic parameters that characterize all information storage devices known today:
- capacity (volume);
- speed (data access speed, reading and writing information);
- interface (connection method, controller type).
Capacity is the total amount of information that can be written and stored on a hard drive. The HDD industry is developing so fast that today hard drives with volumes of the order of 2 TB and above have already come into use. And, as it is believed, this is not the limit.
The interface is the most significant feature. It determines exactly how the device is connected to the motherboard, which controller is used, how reading and writing is performed, etc. The main and most common interfaces are IDE, SATA and SCSI.
Drives with an IDE interface are not expensive, but the main drawbacks include a limited number of simultaneously connected devices (maximum four) and a low data transfer rate (even if Ultra DMA direct memory access or Ultra ATA protocols (Mode 2 and Mode 2 and Mode 2) are supported. 4).Although, as it is believed, their use allows you to increase the read / write speed to the level of 16 Mb / s, but in reality the speed is much lower.In addition, to use the UDMA mode, you need to install a special driver, which, in theory, should be supplied in complete with motherboard.
Speaking about what is the principle of operation of a hard drive and characteristics, one cannot ignore and which is the successor to the IDE ATA version. The advantage of this technology is that the read/write speed can be increased up to 100 Mb/s by using the high-speed Fireware IEEE-1394 bus.
Finally, the SCSI interface is the most flexible and fastest compared to the previous two (write/read speed reaches 160 Mb/s and more). But these hard drives are almost twice as expensive. But the number of simultaneously connected storage devices is from seven to fifteen, the connection can be made without de-energizing the computer, and the cable length can be about 15-30 meters. Actually, this type of HDD is mostly used not in user PCs, but on servers.
Performance, which characterizes the transfer rate and I/O throughput, is usually expressed in terms of transfer time and amount of sequential data transferred, and is expressed in Mbps.
Some additional options
Speaking about what is the principle of operation of a hard drive and what parameters affect its operation, one cannot ignore some additional characteristics that may affect the performance or even the life of the device.
Here in the first place is the rotation speed, which directly affects the search and initialization (recognition) time of the desired sector. This so-called hidden time search - the interval during which the desired sector turns to the reading head. Today, several standards have been adopted for spindle speed expressed in revolutions per minute with dwell times in milliseconds:
- 3600 - 8,33;
- 4500 - 6,67;
- 5400 - 5,56;
- 7200 - 4,17.
It is easy to see that the higher the speed, the less time is spent on searching for sectors, and in physical terms - on disk rotation until the required platter positioning point is set for the head.
Another parameter is the internal transfer rate. On the outer tracks, it is minimal, but increases with a gradual transition to the inner tracks. Thus, the same defragmentation process, which is moving frequently used data to the fastest areas of the disk, is nothing more than moving it to an internal track with a faster read speed. The external speed has fixed values and directly depends on the interface used.
Finally, one of the important points is related to the fact that the hard disk has its own cache memory or buffer. In fact, the principle of operation of a hard disk in terms of buffer use is somewhat similar to RAM or virtual memory. The larger the amount of cache memory (128-256 KB), the faster the hard drive will work.
Main requirements for HDD
There are not so many basic requirements that in most cases apply to hard drives. The main thing is long service life and reliability.
The main standard for most HDDs is considered to be a service life of about 5-7 years with an operating time of at least five hundred thousand hours, but for high-end hard drives this figure is at least a million hours.
As for reliability, the S.M.A.R.T. self-test function is responsible for this, which monitors the status of individual elements of the hard drive, carrying out continuous monitoring. Based on the collected data, even a certain forecast of the appearance of possible faults further.
It goes without saying that the user should not be left out. So, for example, when working with the HDD, it is extremely important to observe the optimal temperature regime(0 - 50 ± 10 degrees Celsius), avoid shocks, bumps and falls of the hard drive, dust or other small particles getting into it, etc. By the way, many will be interested to know that the same particles of tobacco smoke are about twice as large the distance between the reading head and the magnetic surface of the hard drive, and a human hair - 5-10 times.
Initialization issues in the system when replacing a hard drive
Now a few words about what actions should be taken if, for some reason, the user changed the hard drive or installed an additional one.
We will not fully describe this process, but will dwell only on the main stages. First, you need to connect the hard drive and see in the BIOS settings whether new hardware has been detected, in the disk administration section, initialize and create a boot entry, create a simple volume, assign an identifier (letter) to it and format it with a choice of file system. Only after that the new "screw" will be completely ready for work.
Conclusion
That, in fact, is all that briefly concerns the basics of the functioning and characteristics of modern hard drives. Principle of operation external hard disk was not considered fundamentally here, since it practically does not differ in any way from what is used for stationary HDDs. The only difference is only in the method of connecting an additional drive to a computer or laptop. The most common is the connection via a USB interface, which is directly connected to the motherboard. At the same time, if you want to ensure maximum performance, it is better to use the USB 3.0 standard (the port inside is colored blue), of course, provided that the external HDD itself supports it.
For the rest, it seems that many have at least a little understood how a hard drive of any type functions. Perhaps, too many topics were given above, even from a school physics course, however, without this, it will not be possible to fully understand all the basic principles and methods inherent in the production and application of HDDs.
How is a hard drive arranged? What are hard drives? What role do they play in a 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- short name for " Hard Disk Drive". You will also meet English HDD- and slang Winchester or abbreviated Screw.
V computer hard The disk is responsible for storing data. The Windows operating system, programs, movies, photos, documents, all the 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 the processor or video card fails, they can be bought and replaced. But lost family photos from last summer's vacation, or a year's worth of accounting data for a small business, are not so easy to recover. Therefore, the reliability of data storage is given special attention.
Why is a rectangular metal box called a disk? To answer this question, we need to look inside and find out how a hard drive works. In the picture below you can see what parts a hard drive consists of and what functions each part performs. Click to enlarge. (Taken from itc.ua)
I also suggest watching an excerpt from the Discovery Channel program about how a hard drive works and works.
Three more facts you need to know about hard drives.
- The hard drive is the slowest part of a computer. When the computer freezes, pay attention to the hard drive activity indicator. If it blinks frequently or stays on, then the hard drive is executing the commands of one of the programs, while all the others are idle, waiting for their turn. If the operating system does not have enough high-speed RAM to run the program, it uses hard disk space, which greatly slows down the entire computer. Therefore, one way to increase the speed of your computer is to increase the amount of RAM.
- The hard drive is also the most fragile part of a computer. As you learned from the video, the engine spins the disk up to several thousand revolutions per minute. In this case, the magnetic heads "hover" above the disk in the air flow created by the rotating disk. The distance between the disk and heads in modern devices is about 10 nm. If the disk is subjected to shock or shock at this point, the head may touch the disk and damage the surface with data stored on it. As a result, the so-called bad blocks" - unreadable areas, due to which the computer cannot read any file or boot the system. In the off state, the heads "park" outside the working area and overload from impact is not so terrible for the hard drive. Please do it backups important data!
- The capacity of the hard drive is often slightly smaller than what the seller or manufacturer specifies. The reason is that manufacturers indicate the size of the disk, based on the fact that there are 1,000,000,000 bytes in one gigabyte, while there are 1,073,741,824 of them.
Buying a hard drive
If you decide to increase the amount of information storage in your computer by connecting extra hard disk or replacing the old one with a more spacious 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 connecting hard drive supports motherboard. By far the most widely used standards SATA and outliving its age IDE. They are easy to distinguish by appearance. The picture on the left shows a fragment of the motherboard, which is equipped with both types of connectors, but yours will most likely be one of them.
There are three versions of the interface SATA. They differ in data transfer speed. SATA, SATA II and SATA III at speeds of 1.5, 3 and 6 gigabytes per second, respectively. All interface versions SATA look the same and are compatible with each other. You can connect them in any combination, as a result, the data transfer rate will be limited to the slower version. At the same time, the speed of the hard drive is even slower. Therefore, the potential of fast interfaces can be revealed only with the advent of new high-speed drives.
If you decide to purchase an additional hard SATA drive, check if you have an interface cable like in the picture. It is not sold with a CD. (They are usually bundled with the motherboard.) Also, among the power supply connectors, there should 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, the capacity. As I mentioned above, please note that it will be slightly less than stated. The operating system and programs require 100 - 200 gigabytes, which is quite a bit by modern standards. How much additional space you may need, you can determine empirically. Large volumes may be required, for example, for video recording High Quality. Modern films in HD format reach several tens of gigabytes.
In addition, among the main parameters indicate:
- Form Factor- disk size. 1.8" and 2.5" disks 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 desktop computer. But small drives are made with an emphasis on compactness and low power consumption, and in terms of performance they are inferior to larger models. And they cost more.
- RPM- disk rotation speed. Measured in revolutions per minute ( RPM- short for revolutions per minute). The faster the rotation speed, the faster the disk writes and reads information. But it also consumes more energy. Today, the most common discs with 5400RPM and 7200RPM. Lower RPMs are more common in laptop drives, high capacity drives (greater than two terabytes), and so-called "green" drives, named for their reduced power consumption. There are also hard drives with a rotational speed 10000RPM and 15000RPM. They are designed to work in highly loaded servers and have an increased reliability resource, but they also cost much more than conventional ones.
- Manufacturer. On the this moment there are several large manufacturers in the storage market. Among them there is quite tough competition, so they are in no way inferior to each other in quality. Therefore, you can choose any of the well-known names: Hitachi, HP, Seagate, Silicon Power, Toshiba Transcend, Western Digital.
Many of you know that all the information on the computer, presented in the form of files and folders, is stored on the hard drive. But, what is a hard drive and what it is intended for, not many will correctly answer. It is very difficult for people who are far from programming to imagine how information can be stored on some kind of piece of iron. This is not a box or a piece of paper on which this very information can be written down and hidden in a box. Yes, a hard drive is not a box with a letter.
A hard disk (HDD, HMDD-from the 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 photos, pictures, letters, books. various formats, music, movies, etc. Outwardly, this device does not look like a disk at all. Rather, it looks like a small rectangular iron box.
The internals of a hard drive are like an old turntable.
Inside this metal box, there are round aluminum or glass disk plates located on the same axis, along which the reading head moves. Unlike a player, the hard disk head does not touch the surface of the platters during operation.
For convenience, the hard disk is divided into several sections. This division is conditional. This is done using the operating system or special programs. The new partitions are called logical drives. They are assigned the letters C, D, E or F. It is usually installed on the C drive, and the files and folders are stored on other drives so that your files and folders do not suffer if the system crashes.
Watch a video about what a hard drive is:
Key Features of Hard Drives
- Form Factor is the width of the hard drive in inches. Standard size for desktop computer 3.5 inches, and for laptops 2.5 inches;
- Interface- Modern computers use various versions of SATA connections to the motherboard. SATA, SATA II, SATA III. Older computers use the IDE interface.
- Capacity- it maximum amount information that a hard drive can store is measured in gigabytes;
- Spindle speed is the number of spindle revolutions per minute. The faster the disk spins, the better. For operating systems, you need to install drives of 7200 rpm and higher, and for file storage, you can install drives with a lower speed.
- MTBF is the mean time between failures as calculated by the manufacturer. The larger it is, the better;
- Random access time is the average value of the time required for the head to position on an arbitrary section of the plate. The value is not constant.
- impact resistance is the ability of a hard drive to withstand pressure changes and shocks.
- Noise level, which the disc emits during operation is measured in decibels. The smaller it is, the better.
Already there SSD drives(solid-state drive in simple translation- solid-state drive), which have neither a spindle nor platters. This is a storage device based on memory chips.
SSD drives are perfectly quiet and have very good read and write speeds. But they are still very expensive and not very reliable, so they are installed only under operating systems, and IDE and SATA hard drives are used to store files.
The hard drive, or hard drive, is the main and very important part of the computer. It stores not only the operating system that controls the computer, but also all the information of the client or several clients. It often happens that the value of information is many times greater than not only the cost of the hard drive itself, but also the computer as a whole. Therefore, the security of information largely depends on the quality and reliability of such a drive. A modern hard drive looks like the one shown in the picture.
What is a Winchester?
So, what is a drive after all, on the performance of which the well-being and good mood of its owner depends? In fact, a hard drive is a high-tech equipment that stores digital information even when the computer is turned off.
To be more precise, the hard drive consists of several magnetic disks, on which information is applied and read using a magnetic head. These heads, along with magnetic disks are in a vacuum, which allows the drive to work without the influence of the external environment on the process of writing and reading information.
What types of hard drives are there?
So, we found out that a hard drive is an information storage device for a computer. Now let's see what types of HDDs are. First of all, it should be noted that hard drives can be divided into two categories:
- External drives that can be connected to any computer via a USB interface. In some ways, they resemble a flash drive, only larger. Such hard drives do not need special software.
- Internal HDD drives are installed inside computers and have specific connectors for both power and information transfer.
Internal HDDs are also divided into several categories. There are several criteria by which a hard drive can be classified. This is the physical size of the hard drive. There are three sizes:
- 5.5 inches. Typically, hard drives of this size are used in desktop computers, where there is a lot of free space.
- 3.5 inches is used mainly in laptops, where space is limited, and a large amount of memory is needed.
- 2.5 inches are used in ultrabooks where space is very limited.
Another sign by which drives are classified is the data exchange protocol between the hard drive and the computer. What protocols can the hard drive use? They are as follows:
- IDE is an old version of the protocol that was used mainly on computers and laptops before 2000.
- SCSI is a contemporary of IDE, a faster version of drive management that was used primarily in server machines. Required special drivers to use such hard drives.
- SATA is a modern version of the protocol that has several options and has a high speed of writing and reading information. It is used in almost all modern computer systems.
Hard drive problems
One of the most frightening messages that you can see on the screen says that the computer does not see the hard drive. Why does this scare computer users so much? With such a malfunction, the device does not load the operating system; accordingly, practically no actions provided for by this system can be performed.
What can cause such a malfunction? The simplest problem leading to this result is a violation of the integrity of the power loops or the system interface. Often, dust or dirt getting inside such a connector leads to this malfunction. And most experienced users are not particularly frightened when such a message appears, but simply reconnect the power and interface connectors. This inscription may look something like the one shown in the photo above.
Hard drive not visible to BIOS
When such a malfunction occurs, the first thing to determine is whether the this problem physical or software. How to find out? After a message appears stating that the computer does not see the hard drive, you need to reboot the machine and enter the BIOS. What is a BIOS? This is a program that is stored in the ROM of a computer motherboard. It is loaded even before the operating system and determines the peripherals that the motherboard will work with. For BIOS boot you must press the corresponding key on the keyboard, usually the DEL or F2 button. After entering the BIOS, you can see the following picture.
This photo shows that the BIOS did not detect on the computer hard drives. In this case, the problem described above could occur, and the computer, being disconnected from the power cable or interface, is invisible to the BIOS. On the other hand, any malfunction in the hard drive control board will lead to such a problem. At the same time, if it is possible to solve this problem, then only in the appropriate service center. It is almost impossible to eliminate it on your own at home.
Windows 7 does not see the hard drive
But there are times when the hard drive is visible to the BIOS, but the operating system does not boot or Windows is constantly rebooting. In what cases does this happen? Then, when one of the system files was deleted while working with the operating system, or an error occurred during rewriting, and the file is not read correctly. Physical damage to the hard drive, scratching or chipping of the disk surface may also occur. If one of the system files was located in this place, then the operating system will not be able to read it and will issue, as system administrators say, blue screen death, which prompts you to reboot the system. If the error persists, it is best to contact the system administrator. Sometimes such software errors are easy enough to fix without reinstalling the operating system. But it happens that they are fatal, and they can only be fixed with a complete reinstallation of the system. To solve this kind of problems, system utilities are usually used that deal with the restoration of software errors. What are these programs?
Hard drive software errors
There are quite a few programs for recovering software errors that can be divided into two categories. The first includes utilities that are inside the system, and they can be used after the operating system is fully loaded. These are sets of programs for servicing hard drives.
For example, how to maintain a Windows 7 hard drive? You can service your drive directly from the program. To do this, just go to "My Computer" and select the disk that we want to serve in it. Click on the "Properties" tab and see the following picture, shown in the photo above.
Hard drive maintenance programs
As you can see in the picture, the user is offered three utilities:
- Check for errors.
- Disk archiving.
Errors are corrected only by the first program, and the rest will simply serve this disk. But there are programs that work without an operating system. The advantage of such utilities is that they can serve the disk even when the operating system does not boot. For example, one of these programs is called FDISK and was developed by Microsoft as a disk maintenance utility before installing the operating system. Used by experienced users computer technology Norton Disk Doctor, and there are actually quite a lot of such programs, so the choice largely depends on the preferences of a particular person. Before installing Windows from a hard drive, it is advisable to service it with a similar program and correct possible errors.
Hard drive recovery
Often, many users are faced with the problem of recovering data on a problematic hard drive. As mentioned above, often the information stored on it is valued much more than the hard drive itself. Therefore, the work of recovering lost data is not only valuable, but also highly paid. Much depends on how the information disappeared. It is important to remember how Windows deletes information from the hard drive.
The operating system does not erase the information that the user wants to remove. It simply removes the hard drive's table of contents, which allows you to find this information. Such a table of contents is called a FAT table. And if after that no other information was written to the body of the Windows 10 hard drive, then it is quite easy to restore it. There are many programs out there that can do the job. According to many users, one of the best is Acronis Recovery Expert.
Hard drive backup
Be that as it may, not a single user wants to be constantly under the threat that valuable information is in danger. Therefore, efforts are made to minimize risks. What can be done? Backup useful information of the hard drive as a whole or hard disk helps solve this problem.
What are the backup methods?
- In manual mode. The user independently chooses what information and when the program will save. Some companies in their own offices prefer to back up data at the end of the shift. But at the same time, there is a danger of losing information that has accumulated during the day.
- Backup in automatic mode. In this case, the program is invested in how often and what should be copied and saved.
- Creation of a mirror RAID array, which stores all the information from the main hard drive in parallel on another hard drive. If the latter fails, you can easily use the mirror.
Hard disk selection
Paying great attention to the safety of information, do not forget about the choice of the manufacturer of the hard drive, as well as technical parameters characterizing the quality of this hard drive. If we talk about the brand of the drive manufacturer, then it is worth choosing a more well-known company, although such a hard drive will cost a little more. Some users prefer Seagate.
If we talk about technical parameters, then all things being equal, you should pay attention to the speed of reading and writing information. Sometimes this data will help you make a choice in favor of a particular hard drive.
Summarize
So, a hard drive is a storage device of very valuable and important information in a computer. Therefore, it is necessary to make a lot of efforts in order to choose a high-quality hard drive. You should also take care of regular maintenance of your device. In addition, it is important to pay attention to the security of information, if any, on your computer. If you make all these efforts, then your hard drive will serve you for a long time, and the information on it will be completely safe. The operation of your device is completely in your hands, so take all measures for its normal functioning.
The hard disk drive is almost one of the most important elements modern computer. Since it is designed primarily for long-term storage of your data, it can be games, movies and other large files stored on your PC. And it would be a pity 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 - a hard drive.
In this article, you will learn about the operation of the hard drive, its components and specifications Oh.
Typically, 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 desktop computers and even some models of laptops and tablets, they can be easily replaced.
Figure: Hard drive without top cover
The note!
Why are hard drives sometimes called a hard drive and what do they have to do with firearms. Sometime in the 1960s, IBM released a high-speed hard drive at that time with a development number of 30-30. Which coincided with the designation of the famous Winchester rifled weapon, and therefore this term was soon fixed in computer jargon. But in fact, hard drives have nothing to do with real hard drives.
How a hard drive works
Recording and reading of information located on the concentric circles of the hard disk, divided into sectors, is carried out by means of universal write/read heads.
All sides of the disk provide their own track for writing and reading, but the heads are located on a common drive for all disks. For this reason, the heads move synchronously.
YouTube Video: Open Hard Drive Operation
The normal operation of the drive does not allow contact 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 sink to the magnetic surface.
During hard disk operation, a small air gap forms between the surface of the rotating platter and the head. If a speck of dust enters this gap or the device is shaken, there is a high chance that the head will collide with a rotating surface. A strong impact can cause head failure. The result of this output may be damage to several bytes, or the device may be completely inoperable. 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 periodic shaking of the heads.
Some modern drives use a loading / unloading mechanism that does not allow the heads to touch 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 drive. All available 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 comes down to creating a table of contents for the disk and the file system (FAT, NTFS, etc.). Only low-level formatting, during which the disk is divided into tracks and sectors, can be attributed to "real" formatting. With the FORMAT DOS command, a floppy disk is subjected to both types of formatting at once, while a hard disk is only high-level formatted.
In order to produce low-level formatting on the hard disk, you need to use a special program, most often provided by the disk manufacturer. Formatting floppy disks with FORMAT involves performing both operations, while in the case of hard disks, the above operations must be performed separately. Moreover, the hard disk is subjected to a third operation - the creation of partitions, which are necessary condition for use on the same PC with more than one operating system.
The organization of several partitions makes it possible to install on each of them its own operating infrastructure with a separate volume and logical disks. Each volume or logical drive has its own letter designation (for example disk C,D or E).
What is a hard drive made of?
Almost every modern hard drive includes the same set of components:
discs(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(a device that rotates disks);
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 HDD components).
A sealed box - HDA - is most often used as a housing for disks, heads, a head drive mechanism and a disk drive motor. Usually this box is a single unit, which is almost never opened. Other non-HDA components such as configuration items, printed circuit board, and front panel, - removable.
Automatic head parking and control system
In the event of a power outage, a contact parking system is provided, the task of which is to lower the bar with heads onto the discs themselves. Regardless of the fact that the drive withstands tens of thousands of ascents and descents of reading heads, all this must take place in areas specially designated for these actions.
During constant ascents and descents, inevitable abrasion of the magnetic layer occurs. If the drive is subjected to shock after wear, then most likely damage to the disk or heads will occur. To prevent the above troubles, modern drives are equipped with a special loading / unloading mechanism, which is a plate that is placed on the outer surface of hard drives. This measure prevents the head and the magnetic surface from touching even if the power is turned off. When the voltage is turned off, 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 filter and a recirculation filter. What distinguishes 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 drives used the technology of constantly moving air in and out of the case, using a filter that needed to be changed periodically.
The developers of modern drives had to abandon this scheme, and therefore the recirculation filter, which is located in the sealed HDA case, is used only to filter the air inside the box from the smallest particles trapped inside the case. Regardless of all precautions taken, small particles are still formed after repeated “landing” and “takeoffs” of the heads. Taking into account the fact that the case of the drive is distinguished by its tightness and air is pumped in it, it continues to function even in highly polluted environments.
Interface connectors and connections
Many modern hard drives are equipped with several interface connectors designed to connect to a power source and to the system as a whole. As a rule, the drive contains at least three types of connectors:
interface connectors;
connector for power supply;
ground connector.
Interface connectors deserve special attention, since they are designed to receive/transmit commands and data by the drive. Many standards do not exclude the possibility of connecting multiple drives to the same 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 common due to its low cost. Technically, this interface is similar to the 16-bit ISA bus. The subsequent development of IDE standards contributed to an increase in 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 replaced the IDE, which is physically a unidirectional line used for serial data transfer. Being in compatibility mode is similar to the IDE interface, however, the presence of a "native" mode allows you to take advantage of an additional set of features.
SCSI- a universal interface that was actively used on servers to connect HDDs and other 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 needed to connect external hard drives. Exchange of information in this case occurs through the USB Mass Storage protocol.
firewire- a connector similar to USB, is required to connect an external HDD.
fiber channel- an interface used by high-end systems due to the high data transfer rate.
Hard drive quality metrics
Capacity- the amount of information held 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 transfer of information;
Reliability- an indicator determined by the mean time between failures.
Physical capacity limits
Maximum capacity used hard drive, depends on a number of factors, which include the interface, drivers, operating system and file system.
The first ATA drive, released in 1986, had a capacity limit of 137 GB.
Different BIOS versions also contributed to a decrease in the maximum capacity of hard drives, and therefore systems compiled before 1998 had a capacity of up to 8.4 GB, and systems released before 1994 had 528 MB.
Even after solving problems with the BIOS, the capacity limit of drives with an 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 an increase in storage capacity up to 144 GB. Such a solution made it possible to bring to light drives with PATA and SATA interfaces, in which the amount of information they can hold 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.
So, for example, DOS did not recognize hard drives with a capacity exceeding 8.4 GB, since access to the drives in this case was performed through LBA addressing, while in DOS 6.x and earlier versions only CHS addressing was supported.
There is also a hard disk capacity limit if Windows 95 is installed. The maximum value for this limit is 32 GB. In addition, updated versions of Windows 95 only support the FAT16 file system, which, in turn, imposes a 2 GB size limit on partition sizes. From this it follows that in the case of using a 30 GB hard disk, it must be divided into 15 partitions.
The limitations of the Windows 98 operating system 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 pay attention to is the type of interface being used. Recently, every computer has begun to use as an improved and faster interface SATA.
Second no less important point— the amount of free space on the hard drive. Its minimum value today is only 80 GB, while the maximum is 4 TB.
Another important characteristic in the case of purchasing a laptop is the form factor of the hard drive.
The most popular in this case are models whose size is 2.5 inches, while in desktop PCs the size is 3.5 inches.
Do not neglect the spindle speed, the minimum values are 4200, the maximum ones are 15000 rpm. All of the above characteristics have a direct impact on the speed of the hard drive, which is expressed in Mb / s.
Hard drive speed
Of no small importance are the speed indicators of the hard drive, which are determined by:
Spindle speed, 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 spent by the hard drive from receiving a command to transmitting information over the interface. Most often I figure the average and maximum values.
Head positioning time. This value specifies the time it takes for the heads to move and set from one track to another track.
Bandwidth or disk performance during serial transfer of large amounts of data.
Internal baud rate or the rate of information transmitted from the controller to the heads.
External baud rate or the rate of information transmitted 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 PATA and SATA interfaces, and also work in personal computers with Windows operating system (from NT to Vista).
S.M.A.R.T. calculates and analyzes the status of connected hard drives at regular intervals, regardless of whether the operating system is running or not. After the analysis has been carried out, the diagnostic result icon is displayed in the right corner of the taskbar. Based on the results obtained during the S.M.A.R.T. diagnostics, the icon may indicate:
On 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 value of zero. The above state of the hard drive is not considered pre-crash, however, if this hard drive contains important information, it is recommended that you save it to another media as often as possible or replace the HDD.
The fact that one or more status indicators do not meet the threshold value, while the Pre-Failure / Advisory parameters have an active value. According to 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
Such an indicator as the reliability of data storage is one of the most important characteristics of a 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 reliability of each disk is directly affected by the operating conditions and the device itself. Sometimes manufacturers supply the market with a completely “raw” product, and therefore it is impossible to neglect backup and completely rely on the hard drive.
Cost and price
Every day the cost of HDD becomes less and less. So, for example, today the price of a 500 GB ATA hard disk is on average $120, in comparison, in 1983 a 10 MB hard drive cost $1,800.
From the above statement, we can conclude that the cost of the HDD will continue to fall, and therefore in the future everyone will be able to purchase fairly capacious drives at affordable prices.