Information is recorded on magnetic disks. Flexible magnetic disks. What is formatting

Magnetic disks Computers are used for long-term storage of information (it is not erased when the computer is turned off). In this case, during operation, data can be deleted, while others can be written.

There are hard and flexible magnetic disks. However, floppy disks are now used very rarely. Floppy disks were especially popular in the 80s and 90s of the last century.

Floppy disks(floppy disks), sometimes called floppy disks, are magnetic disks housed in square plastic cassettes measuring 5.25 inches (133 mm) or 3.5 inches (89 mm). Floppy disks allow you to transfer documents and programs from one computer to another, store information, and make archival copies of information contained on the hard drive.

Information on a magnetic disk is written and read by magnetic heads along concentric tracks. When writing or reading information, the magnetic disk rotates around its axis, and the head is moved to the desired track using a special mechanism.

3.5" floppy disks have a capacity of 1.44 MB. This type floppy disks are the most common nowadays.

Unlike floppy disks hard drive allows you to store large amounts of information. Capacity hard drives modern computers can amount to terabytes.

The first hard drive was created by IBM in 1973. It allowed storing up to 16 MB of information. Since this disk had 30 cylinders divided into 30 sectors, it was designated as 30/30. By analogy with automatic rifles with a caliber of 30/30, this disc was nicknamed “Winchester”.

A hard drive is a sealed iron box, inside of which there is one or more magnetic disks along with a read/write head unit and an electric motor. When you turn on the computer, the electric motor spins the magnetic disk to high speed (several thousand revolutions per minute) and the disk continues to rotate as long as the computer is turned on. Special ones “hover” above the disk magnetic heads, which write and read information in the same way as on floppy disks. The heads float above the disk due to its high rotation speed. If the heads touched the disk, the disk would quickly fail due to friction.

When working with magnetic disks, the following concepts are used.

Track– a concentric circle on a magnetic disk, which is the basis for recording information.

Cylinder is a set of magnetic tracks located one above the other on all working surfaces of hard drives.

Sector– a section of a magnetic track, which is one of the main units of information recording. Each sector has its own number.

Cluster- the minimum element of a magnetic disk that the operating system operates when working with disks. Each cluster consists of several sectors.

In the 19th century, magnetic recording was invented. Initially it was used only to store sound.

On computers of the first and second generations, magnetic tape was used as the only type of removable media for external memory devices. One reel of magnetic tape held approximately 500 KB of information.

Since the early 1960s, magnetic disks have appeared: aluminum or plastic disks coated with a thin magnetic powder layer several microns thick. Information on the disk is located along circular concentric tracks.

The device that provides recording/reading of information is called an information storage device or disk drive. Magnetic disks are hard and flexible, removable and built into the computer drive (traditionally called hard drives).

Magnetic principle of recording and reading information

In floppy magnetic disk drives (FMD) and hard magnetic disk drives (HDD), or hard drives, the basis for recording information is magnetization of ferromagnets in a magnetic field, information storage is based on the conservation of magnetization, and information reading is based on the phenomenon electromagnetic induction.

In the process of recording information on flexible and hard magnetic disks, the drive head with a core made of soft magnetic material (low residual magnetization) moves along the magnetic layer of the hard magnetic medium (high residual magnetization). The magnetic head receives sequences of electrical pulses (sequences of logical ones and zeros), which create a magnetic field in the head. As a result, the elements of the surface of the carrier are sequentially magnetized (logical one) or not magnetized (logical zero). When reading information when the magnetic head moves over the surface of the carrier, magnetized areas of the carrier cause current pulses in it (the phenomenon of electromagnetic induction). Sequences of such pulses are transmitted along the highway to RAM computer.

In the absence of strong magnetic fields and high temperatures, the carrier elements can retain their magnetization for a long time (years and decades).

Floppy magnetic disks

Until recently, personal computers were equipped with a floppy disk drive (FMD), which is called in price lists FDD– Floppy Disk Drive (floppy disk drive). Floppy disks themselves are called floppy disks. The most common type of floppy disk, 3.5 inches (89 mm) in diameter, holds 1.44 MB of information.

The 3.5-inch floppy disk itself, with a magnetic layer applied to it, is enclosed in a hard plastic sleeve that protects the floppy disk from mechanical damage and dust.

To provide access for the magnetic read-write heads to the floppy disk, there is a slot in its plastic case that is closed with a metal latch. The latch automatically retracts when a floppy disk is inserted into the drive.

In the center of the floppy disk there is a device for gripping and rotating the disk inside the plastic case. The floppy disk is inserted into the disk drive, which rotates it at a constant angular velocity. In this case, the magnetic head of the drive is installed on a specific concentric track of the disk (track), on which information is written or from which information is read.

Both sides of the floppy disk are covered with a magnetic layer and each side has 80 concentric tracks (tracks) for recording data. Each track is divided into 18 sectors, and each sector can contain a data block of size 512 bytes.

When performing read or write operations, the floppy disk rotates in the drive, and the read-write heads are installed on the desired track and access the specified sector.

The speed of writing and reading information is about 50 KB/s. The floppy disk rotates in the drive at a speed of 360 rpm.

In order to preserve information, flexible magnetic disks must be protected from exposure to strong magnetic fields and heat, since such physical effects can lead to demagnetization of the media and loss of information.

Floppy disks are now becoming obsolete.

Hard magnetic disks

Hard magnetic disk drive (HDD) or, as it is more often called, a hard drive or hard drive ( Hard Disk), is the main data storage location in personal computer. In price lists, hard drives are indicated as HDD - Hard Disk Drive(Drive hard drive).

The origin of the name “Winchester” has two versions. According to the first, IBM developed a hard drive with 30 MB of information on each side, codenamed 3030. Legend has it that a rifle like the Winchester 3030 conquered the West. The developers of the device had the same intentions.

According to another version, the name of the device comes from the name of the city of Winchester in England, where the technology for manufacturing a floating head for hard drives was developed in the IBM laboratory. The read-write head made using this technology, due to its aerodynamic properties, seems to float in the air flow that is formed during the rapid rotation of the disk.

Winchester is one or more hard (aluminum, ceramic or glass) disks placed on one axis, coated with magnetic material, which, together with the read-write heads, electronics and all the mechanics necessary for rotating the disks and positioning the heads, are enclosed in a non-separable sealed case.

Mounted on an electric motor spindle, the disks rotate at high speed (7,200 rpm), and information is read/written by magnetic heads, the number of which corresponds to the number of surfaces used to store information.

The speed of writing and reading information from hard drives is quite high – it can reach 300 MB/s.

The capacity of modern hard drives (as of November 2010) reaches 3,000 GB (3 Terabytes).

There are portable hard drives - they are not installed inside the system unit, but are connected to the computer via a parallel port or via a USB port.

Hard drives use rather fragile and miniature elements (media platters, magnetic heads, etc.), therefore, in order to preserve information and performance hard drives must be protected from impacts and sudden changes in spatial orientation during operation.

Plastic cards

Plastic cards have become widespread in the banking system. They also use the magnetic principle of recording information with which ATMs and cash registers associated with the banking information system operate.

A hard magnetic disk drive (HDD) \ HDD (Hard Disk Drive) \ hard drive (media) is a material object capable of storing information.

Information storage devices can be classified according to the following criteria:

• method of storing information: magnetoelectric, optical, magneto-optical;
• type of storage medium: drives on floppy and hard magnetic disks, optical and magneto-optical disks, magnetic tape, solid-state memory elements;
• the method of organizing access to information - direct, sequential and block access drives;
• type of information storage device - embedded (internal), external, stand-alone, mobile (wearable), etc.

A significant part of the information storage devices currently in use is based on magnetic media.

Hard drive device

The hard drive contains a set of plates, most often representing metal disks, coated with a magnetic material - platter (gamma ferrite oxide, barium ferrite, chromium oxide...) and connected to each other using a spindle (shaft, axis).
The discs themselves (approximately 2 mm thick) are made of aluminum, brass, ceramics or glass. (see pic)

Both surfaces of the discs are used for recording. Used 4-9 plates. The shaft rotates at a high constant speed (3600-7200 rpm)
Rotation of disks and radical movement of heads is carried out using 2 electric motors.
Data is written or read using write/read heads one for each surface of the disk. The number of heads is equal to the number of working surfaces of all disks.

Information is written to the disk in strictly defined places - concentric tracks (tracks) . The tracks are divided into sectors. One sector contains 512 bytes of information.

Data exchange between RAM and NMD is carried out sequentially by an integer (cluster). Cluster- chains of consecutive sectors (1,2,3,4,...)

Special engine using a bracket, positions the read/write head over a given track (moves it in the radial direction).
When the disk is rotated, the head is located above the desired sector. Obviously, all heads move simultaneously and read information; data heads move simultaneously and read information from identical tracks on different drives.

Hard drive tracks with the same serial number on different hard drive drives are called cylinder .
The read-write heads move along the surface of the platter. The closer the head is to the surface of the disk without touching it, the higher the permissible recording density.

Hard drive device

Magnetic principle of reading and writing information

Magnetic information recording principle

The physical foundations of the processes of recording and reproducing information on magnetic media are laid in the works of physicists M. Faraday (1791 - 1867) and D. C. Maxwell (1831 - 1879).

In magnetic storage media, digital recording is made on magnetically sensitive material. Such materials include some varieties of iron oxides, nickel, cobalt and its compounds, alloys, as well as magnetoplasts and magnetoelastas with viscous plastics and rubber, micropowder magnetic materials.

The magnetic coating is several micrometers thick. The coating is applied to a non-magnetic base, which is made from plastics for magnetic tapes and floppy disks, and aluminum alloys and composite substrate materials for hard disks. The magnetic coating of the disk has a domain structure, i.e. consists of many magnetized tiny particles.

Magnetic domain (from Latin dominium - possession) is a microscopic, uniformly magnetized region in ferromagnetic samples, separated from neighboring regions by thin transition layers (domain boundaries).

Under the influence of an external magnetic field, the domains' own magnetic fields are oriented in accordance with the direction of the magnetic field lines. After the influence of the external field ceases, zones of residual magnetization are formed on the surface of the domain. Thanks to this property, information is stored on a magnetic medium in the presence of a magnetic field.

When recording information, an external magnetic field is created using a magnetic head. In the process of reading information, the zones of residual magnetization, located opposite the magnetic head, induce an electromotive force (EMF) in it during reading.

The scheme for writing and reading from a magnetic disk is shown in Fig. 3.1 A change in the direction of the EMF over a certain period of time is identified with a binary unit, and the absence of this change is identified with zero. The specified period of time is called bit element.

The surface of a magnetic medium is considered as a sequence of point positions, each of which is associated with a bit of information. Since the location of these positions is not precisely determined, recording requires pre-applied marks to help locate the required recording positions. To apply such synchronization marks, the disk must be divided into tracks
and sectors - formatting

Organization quick access to information on disk is an important stage of data storage. Quick access to any part of the disk surface is ensured, firstly, by giving it rapid rotation and, secondly, by moving the magnetic read/write head along the radius of the disk.
A floppy disk rotates at a speed of 300-360 rpm, and a hard disk rotates at 3600-7200 rpm.

Hard drive logical device

The magnetic disk is not initially ready for use. To bring it into working condition it must be formatted, i.e. the disk structure must be created.

The structure (layout) of the disk is created during the formatting process.

Formatting magnetic disks includes 2 stages:

1. physical formatting ( low level)
2. logical (high level).

When physically formatting, the working surface of the disk is divided into separate areas called sectors, which are located along concentric circles - paths.

In addition, sectors that are unsuitable for recording data are determined and marked as bad in order to avoid their use. Each sector is the smallest unit of data on a disk and has its own address to allow direct access to it. The sector address includes the disc side number, the track number, and the sector number on the track. The physical parameters of the disk are set.

As a rule, the user does not need to deal with physical formatting, since in most cases hard drives arrive formatted. Generally speaking, this should be handled by a specialized service center.

Low Level Formatting must be done in the following cases:

• if there is a failure in track zero, causing problems when booting from a hard disk, but the disk itself is accessible when booting from a floppy disk;
• if you return to working condition old disk, for example, rearranged from a broken computer.
• if the disk is formatted to work with another operating system;
• if the disk has stopped working normally and all recovery methods have not yielded positive results.

One thing to keep in mind is that physical formatting is a very powerful operation— when it is executed, the data stored on the disk will be completely erased and it will be completely impossible to restore it! Therefore, do not proceed with low-level formatting unless you are confident that you have stored all important data off the hard drive!

After you perform low-level formatting, the next step is to create a partition of the hard drive into one or more logical drives - best way cope with the confusion of directories and files scattered across the disk.

Without adding any hardware elements to your system, you get the opportunity to work with several parts of one hard drive, like multiple drives.
This does not increase the disk capacity, but its organization can be significantly improved. In addition, various logical drives can be used for various operating systems.

At logical formatting The media is finally prepared for data storage through the logical organization of disk space.
The disk is prepared to write files to the sectors created by low level formatting.
After creating the disk partition table, the next stage follows - logical formatting individual parts partitions, hereinafter referred to as logical disks.

Logical drive - This is some area of ​​​​the hard drive that works in the same way as a separate drive.

Logical formatting is a much simpler process than low-level formatting.
To run it, boot from the floppy disk containing the FORMAT utility.
If you have several logical drives, format them all one by one.

During the logical formatting process, the disk is allocated system area, which consists of 3 parts:

• boot sector and partition table (Boot record)
• File Allocation Tables (FAT), in which the numbers of tracks and sectors storing files are recorded
• root directory (Root Directory).

Information is recorded in parts through the cluster. There cannot be 2 different files in the same cluster.
In addition, the disk can be given a name at this stage.

A hard drive can be divided into several logical drives and, conversely, 2 hard drives can be combined into one logical drive.

It is recommended to create at least two partitions (two logical drives) on your hard drive: one of them is allocated for the operating system and software, the second drive is exclusively allocated for user data. Thus the data and system files are stored separately from each other and in the event of an operating system failure there is a much greater likelihood of saving user data.

Characteristics of hard drives

Hard drives (hard drives) differ from each other in the following characteristics:

1. capacity
2. performance – data access time, speed of reading and writing information.
3. interface (connection method) - the type of controller to which the hard drive should be connected (most often IDE/EIDE and various options SCSI).
4. other features

1. Capacity— the amount of information that fits on the disk (determined by the level of manufacturing technology).
Today the capacity is 500 -2000 or more GB. You can never have enough hard drive space.

2. Speed ​​of operation (performance) disk is characterized by two indicators: disk access time And disk read/write speed.

Access time – the time required to move (position) the read/write heads to the desired track and the desired sector.
The average typical access time between two randomly selected tracks is approximately 8-12ms (milliseconds), more fast disks have a time of 5-7ms.
The transition time to the adjacent track (adjacent cylinder) is less than 0.5 - 1.5 ms. It also takes time to turn to the desired sector.
The total disk rotation time for today's hard drives is 8 - 16ms, the average sector waiting time is 3-8ms.
The shorter the access time, the faster the disk will operate.

Read/write speed (throughput input/output) or data transfer rate (transfer)– the transfer time of sequential data depends not only on the disk, but also on its controller, bus types, and processor speed. The speed of slow disks is 1.5-3 MB/s, for fast ones 4-5 MB/s, for the latest ones 20 MB/s.
Hard drives with SCSI interface support a rotation speed of 10,000 rpm. and average search time 5ms, data transfer speed 40-80 Mb/s.

3.Hard drive interface standard - i.e. the type of controller to which the hard drive should be connected. It is located on the motherboard.
There are three main connection interfaces

1. IDE and its various variants

IDE (Integrated Disk Electronic) or (ATA) Advance Technology Attachment
Advantages: simplicity and low cost

Transfer speed: 8.3, 16.7, 33.3, 66.6, 100 Mb/s. As data develops, the interface supports expanding the list of devices: hard drive, super floppy, magneto-optics,
NML, CD-ROM, CD-R, DVD-ROM, LS-120, ZIP.

Some elements of parallelization (gneuing and disconnect/reconnect) and monitoring the integrity of data during transmission are introduced. The main disadvantage of the IDE is the small number of connected devices (no more than 4), which is clearly not enough for a high-end PC.
Today, IDE interfaces have switched to new Ultra ATA exchange protocols. Significantly increasing your throughput
Mode 4 and DMA (Direct Memory Access) Mode 2 allows data transfer at a speed of 16.6 MB / s, but the actual data transfer speed would be much lower.
Standards Ultra DMA/33 and Ultra DMA/66, developed in February 1998. by Quantum have 3 operating modes 0,1,2 and 4, respectively, in the second mode the carrier supports
transfer speed 33Mb/s. (Ultra DMA/33 Mode 2) To ensure such a high speed can only be achieved when exchanging with the drive buffer. In order to take advantage
Ultra DMA standards require that 2 conditions be met:

1. hardware support on the motherboard (chipset) and on the drive itself.

2. to support Ultra DMA mode, like other DMA (direct memory Access).

Requires a special driver for different chipsets. As a rule, they are included in the kit motherboard, if necessary, you can “download” it
from the Internet from the manufacturer's page motherboard.

The Ultra DMA standard is backward compatible with previous controllers operating in a slower version.
Today's version: Ultra DMA/100 (late 2000) and Ultra DMA/133 (2001).

SATA
Replacement IDE (ATA) not other High Speed ​​Serial Bus Fireware (IEEE-1394). Application new technology will allow you to increase the transfer speed to 100Mb/s,
The reliability of the system is increased, this will allow you to install devices without turning on the PC, which is strictly prohibited in the ATA interface.

SCSI (Small Computer System Interface)— devices are 2 times more expensive than regular ones and require a special controller on the motherboard.
Used for servers, publishing systems, CAD. Provide higher performance (speed up to 160Mb/s), wide range connected storage devices.
The SCSI controller must be purchased together with the corresponding disk.

SCSI has an advantage over IDE - flexibility and performance.
Flexibility lies in the large number of connected devices (7-15), and for IDE (4 maximum), a longer cable length.
Performance - high speed transfers and the ability to simultaneously process multiple transactions.

1. Ultra Sсsi 2/3 (Fast-20) up to 40 Mb/s 16-bit version Ultra2 - SCSI standard up to 80 Mb/s

2. Another SCSI interface technology called Fiber Channel Arbitrated Loop (FC-AL) allows you to connect up to 100 Mbps, with a cable length of up to 30 meters. FC-AL technology allows for “hot” connections, i.e. on the go, has additional lines for monitoring and error correction (the technology is more expensive than regular SCSI).

4. Other features of modern hard drives

The huge variety of hard drive models makes it difficult to choose the right one.
In addition to the required capacity, performance is also very important, which is determined mainly by its physical characteristics.
Such characteristics are the average search time, rotation speed, internal and external transfer speed, and cache memory size.

4.1 Average search time.

The hard drive takes some time to move the magnetic head from its current position to the new one required to read the next piece of information.
In each specific situation this time varies depending on the distance the head must move. Typically, specifications provide only averaged values, and the averaging algorithms used by different companies, in particular general case vary, so direct comparison is difficult.

Thus, Fujitsu and Western Digital companies use all possible pairs of tracks; Maxtor and Quantum companies use the random access method. The resulting result can be further adjusted.

The search time for writing is often slightly higher than for reading. Some manufacturers provide only the lower value (for reading) in their specifications. In any case, in addition to the average values, it is useful to take into account the maximum (across the entire disk),
and minimum (i.e., track-to-track) search time.

4.2 Rotation speed

From the point of view of the speed of access to the desired fragment of the recording, the rotation speed affects the amount of the so-called latent time, which is required for the disk to rotate to the magnetic head with the desired sector.

The average value of this time corresponds to half a disk revolution and is 8.33 ms at 3600 rpm, 6.67 ms at 4500 rpm, 5.56 ms at 5400 rpm, 4.17 ms at 7200 rpm.

The value of latent time is comparable to average seek time, so in some modes it can have the same, if not greater, impact on performance.

4.3 Internal baud rate

— the speed at which data is written to or read from the disk. Due to zone recording, it has a variable value - higher on the outer tracks and lower on the inner ones.
When working with long files, in many cases this parameter limits the transfer speed.

4.4 External baud rate

— speed (peak) with which data is transmitted through the interface.

It depends on the interface type and most often has fixed values: 8.3; 11.1; 16.7Mb/s for Enhanced IDE (PIO Mode2, 3, 4); 33.3 66.6 100 for Ultra DMA; 5, 10, 20, 40, 80, 160 Mb/s for synchronous SCSI, Fast SCSI-2, FastWide SCSI-2 Ultra SCSI (16 bits), respectively.

4.5 Whether the hard drive has its own Cache memory and its volume (disk buffer).

The size and organization of Cache memory (internal buffer) can significantly affect the performance of the hard drive. Same as for regular cache memory,
Once a certain volume is reached, productivity growth slows down sharply.

Large-capacity segmented cache memory is relevant for high-performance SCSI drives used in multitasking environments. How more cache, the faster the hard drive works (128-256Kb).

The influence of each parameter on overall performance is quite difficult to isolate.

Hard drive requirements

The main requirement for disks is reliability of operation, guaranteed by a long component life of 5-7 years; good statistical indicators, namely:

• mean time between failures of at least 500 thousand hours ( upper class 1 million hours or more.)
• built-in active monitoring system for the state of disk nodes SMART/Self Monitoring Analysis and Report Technology.

Technology S.M.A.R.T. (Self-Monitoring Analysis and Reporting Technology) is an open industry standard developed at one time by Compaq, IBM and a number of other hard drive manufacturers.

The meaning of this technology is the internal self-diagnosis of the hard drive, which allows you to assess its current condition and inform you about possible future problems that could lead to data loss or failure of the drive.

The condition of all vital disk elements is constantly monitored:
heads, working surfaces, electric motor with spindle, electronics unit. For example, if a signal weakening is detected, the information is rewritten and further observation occurs.
If the signal weakens again, the data is transferred to another location, and the given cluster is placed as defective and unavailable, and another cluster from the disk reserve is made available instead.

When working with hard drive The temperature conditions in which the drive operates must be observed. Manufacturers guarantee trouble-free operation of the hard drive at ambient temperatures ranging from 0C to 50C, although, in principle, without serious consequences you can change the limits by at least 10 degrees in both directions.
With large temperature deviations, an air layer of the required thickness may not be formed, which will lead to damage to the magnetic layer.

In general, HDD manufacturers pay quite a lot of attention to the reliability of their products.

The main problem is foreign particles getting inside the disk.

For comparison: a particle of tobacco smoke is twice the distance between the surface and the head, the thickness of a human hair is 5-10 times greater.
For the head, an encounter with such objects will result in a strong blow and, as a result, partial damage or complete failure.
Outwardly, this is noticeable as the appearance of a large number of regularly located unusable clusters.

Short-term, large accelerations (overloads) that occur during impacts, falls, etc. are dangerous. For example, from an impact the head sharply hits the magnetic
layer and causes its destruction in the corresponding place. Or, conversely, it first moves in the opposite direction, and then, under the influence of elastic force, it hits the surface like a spring.
As a result, particles of magnetic coating appear in the housing, which again can damage the head.

Do not think that under the influence of centrifugal force they will fly away from the disk - the magnetic layer
will firmly attract them to you. In principle, the terrible consequences are not the impact itself (you can somehow come to terms with the loss of a certain number of clusters), but the fact that particles are formed that will certainly cause further damage to the disk.

To prevent such very unpleasant cases, various companies resort to all sorts of tricks. In addition to simply increasing the mechanical strength of the disk components, intelligent S.M.A.R.T. technology is also used, which monitors the reliability of recording and the safety of data on the media (see above).

In fact, the disk is always not formatted to its full capacity; there is some reserve. This is mainly due to the fact that it is almost impossible to produce a carrier
on which absolutely the entire surface would be of high quality, there will definitely be bad clusters (failures). When a disk is low-level formatted, its electronics are configured so that
so that it bypasses these faulty areas, and it is completely invisible to the user that the media has a defect. But if they are visible (for example, after formatting
the utility displays their number other than zero), then this is already very bad.

If the warranty has not expired (and, in my opinion, it is best to buy a HDD with a warranty), then immediately take the disk to the seller and demand a replacement of the media or a refund.
The seller, of course, will immediately begin to say that a couple of faulty areas are not a reason for concern, but do not believe him. As already mentioned, this couple will most likely cause many more, and subsequently the complete failure of the hard drive is possible.

A disk in working condition is especially sensitive to damage, so you should not place the computer in a place where it may be subject to various shocks, vibrations, and so on.

Preparing the hard drive for work

Let's start from the very beginning. Let's assume that you bought a hard drive and a cable for it separately from the computer.
(The fact is that when you buy an assembled computer, you will receive a disk prepared for use).

A few words about handling it. A hard disk drive is a very complex product that contains, in addition to electronics, precision mechanics.
Therefore, it requires careful handling - shocks, falls and strong vibration can damage its mechanical part. As a rule, the drive board contains many small-sized elements and is not covered with durable covers. For this reason, care should be taken to ensure its safety.
The first thing you should do when you receive a hard drive is to read the documentation that came with it - it will probably contain a lot of useful and interesting information. In this case, you should pay attention to the following points:

• the presence and options for setting jumpers that determine the settings (installation) of the disk, for example, determining such a parameter as the physical name of the disk (they may be present, but they may not be present),
• number of heads, cylinders, sectors on disks, precompensation level, and disk type. You must enter this information when prompted by the computer setup program.
  All this information will be needed when formatting the disk and preparing the machine to work with it.
• If the PC itself does not detect the parameters of your hard drive, the bigger problem will be installing a drive for which there is no documentation.
  On most hard drives you can find labels with the name of the manufacturer, the type (brand) of the device, as well as a table of tracks that are not allowed for use.
  In addition, the drive can contain information about the number of heads, cylinders and sectors and the level of precompensation.

To be fair, it must be said that often only its title is written on the disc. But even in this case, you can find the required information either in the reference book,
or by calling the company's representative office. It is important to get answers to three questions:

• How should the jumpers be set in order to use the drive as master\slave?
• How many cylinders and heads are there on the disk, how many sectors per track, what is the precompensation value?
• Which type of disk from those recorded in the ROM BIOS best matches this drive?

With this information in hand, you can proceed to installing the hard drive.

For installing hard disk into your computer, do the following:

1. Disable completely system unit from the power supply, remove the cover.
2. Connect the hard drive cable to the motherboard controller. If you are installing a second disk, you can use the cable from the first one if it has an additional connector, but you need to remember that the operating speed of different hard drives will be compared to the slower side.
3. If necessary, change the jumpers according to the way you use the hard drive.
4. Install the drive on free space and connect the cable from the controller on the board to the hard drive connector with the red stripe to the power supply, power supply cable.
5. Securely secure the hard drive with four bolts on both sides, arrange the cables inside the computer in order so that when closing the cover you do not cut them,
6. Close the system unit.
7. If the PC itself does not detect the hard drive, then change the computer configuration using Setup so that the computer knows that a new device has been added to it.

Hard drive manufacturers

Hard drives of the same capacity (but from different manufacturers) usually have more or less similar characteristics, and the differences are expressed mainly in the design of the case, form factor (in other words, dimensions) and lifespan warranty service. Moreover, special mention should be made about the latter: the cost of information on a modern hard drive is often many times higher than its own price.

If your disk has problems, trying to repair it often only means exposing your data to additional risk.
A much more reasonable way is to replace the faulty device with a new one.
The lion's share of hard drives on the Russian (and not only) market is made up of products from IBM, Maxtor, Fujitsu, Western Digital (WD), Seagate, Quantum.

name of the manufacturer producing this type storage,

Corporation Quantum (www. quantum. com.), founded in 1980, is one of the veterans in the disk drive market. The company is known for its innovative technical solutions, aimed at improving the reliability and performance of hard drives, data access time on the disk and read/write speed on the disk, the ability to inform about possible future problems that could lead to data loss or disk failure.

— One of Quantum’s proprietary technologies is SPS (Shock Protection System), designed to protect the disk from shock.

- built-in DPS (Data Protection System) program, designed to preserve the most valuable thing - the data stored on them.

Corporation Western Digital (www.wdс.com.) Also one of the oldest disk drive manufacturing companies, it has seen its ups and downs in its history.
Company for lately was able to introduce the latest technologies into its disks. Among them, it is worth noting our own development - Data Lifeguard technology, which is a further development of the S.M.A.R.T. system. It attempts to logically complete the chain.

According to this technology, the surface of the disk is regularly scanned during the period when it is not used by the system. This reads the data and checks its integrity. If problems are noted while accessing a sector, the data is transferred to another sector.
Information about bad sectors is entered into an internal defect list, which avoids future entries into bad sectors in the future.

Firm Seagate (www.seagate.com) very famous in our market. By the way, I recommend hard drives from this particular company as they are very reliable and durable.

In 1998, she brought attention to herself again by releasing a series of Medallist Pro discs
with a rotation speed of 7200 rpm, using special bearings for this. Previously, this speed was used only in SCSI interface drives, which made it possible to increase performance. The same series uses SeaShield System technology, designed to improve the protection of the disk and the data stored on it from the influence of electrostatics and shock. At the same time, the impact of electromagnetic radiation is also reduced.

All manufactured discs support S.M.A.R.T technology.
Seagate's new drives include an improved version of its SeaShield system with more capabilities.
It is significant that Seagate announced the highest shock resistance of the updated series in the industry - 300G when not in use.

Firm IBM (www. storage. ibm. com) although until recently it was not a major supplier to Russian market hard drives, but managed to quickly gain a good reputation thanks to its fast and reliable disk drives.

Firm Fujitsu (www.fujitsu.com) is a large and experienced manufacturer of disk drives, not only magnetic, but also optical and magneto-optical.
True, the company is by no means a leader in the market of hard drives with an IDE interface: it controls (according to various studies) approximately 4% of this market, and its main interests lie in the field of SCSI devices.

Terminological dictionary

Since some storage elements playing important role in his work are often perceived as abstract concepts, below is an explanation of the most important terms.

Access time— The period of time required for a hard disk drive to search for and transfer data to or from memory.
The performance of hard disk drives is often determined by access (fetch) time.

Cluster- the smallest unit of space that the OS works with in the file location table. Typically a cluster consists of 2-4-8 or more sectors.
The number of sectors depends on the type of disk. Searching for clusters instead of individual sectors reduces OS time costs. Large clusters provide faster performance
drive, since the number of clusters in this case is smaller, but the space (space) on the disk is used worse, since many files may be smaller than the cluster and the remaining bytes of the cluster are not used.

Controller (Controller)- circuitry, usually located on an expansion card, that controls the operation of the hard disk drive, including moving the head and reading and writing data.

Cylinder- tracks located opposite each other on all sides of all disks.

Drive head- a mechanism that moves along the surface of the hard drive and provides electromagnetic recording or reading of data.

File Allocation Table (FAT)- a record generated by the OS that tracks the placement of each file on the disk and which sectors are used and which are free for writing new data to them.

Head gap— the distance between the drive head and the disk surface.

Interleave— the relationship between the disk rotation speed and the organization of sectors on the disk. Typically, the rotation speed of the disk exceeds the computer's ability to receive data from the disk. By the time the controller reads the data, the next sequential sector has already passed the head. Therefore, data is written to the disk through one or two sectors. Using a special software When formatting a disk, you can change the striping order.

Logical drive- certain parts of the working surface of the hard drive, which are considered as separate drives.
Some logical drives can be used for other operating systems, such as UNIX.

Parking- moving the drive heads to a specific point and fixing them stationary above unused parts of the disk, in order to minimize damage when the drive is shaken when the heads hit the surface of the disk.

Partitioning– operation of dividing a hard disk into logical drives. All disks are partitioned, although small disks may only have one partition.

Disk (Platter)- the metal disk itself, coated with magnetic material, on which data is recorded. A hard drive usually has more than one disk.

RLL (Run-length-limited)- an encoding scheme used by some controllers to increase the number of sectors per track to accommodate more data.

Sector- A disk track division that represents the basic unit of size used by the drive. OS sectors typically contain 512 bytes.

Positioning time (Seek time)- the time required for the head to move from the track on which it is installed to some other desired track.

Track- concentric division of the disk. The tracks are similar to the tracks on a record. Unlike the tracks on a record, which are a continuous spiral, the tracks on a disc are circular. The tracks are in turn divided into clusters and sectors.

Track-to-track seek time— the time required for the drive head to move to the adjacent track.

Transfer rate- the amount of information transferred between the disk and the computer per unit of time. It also includes the time it takes to search for a track.

Magnetic disks (MD) refer to magnetic storage media. As a storage medium, they use magnetic materials with special properties (with a rectangular hysteresis loop) that make it possible to record two magnetic states - two directions of magnetization. Each of these states is associated with binary digits: 0 and 1. Memory media (MD) are the most common external storage devices in PCs. Disks are hard and flexible, removable and built into the PC. A device for reading and writing information on a magnetic disk is called a disk drive.

All disks: both magnetic and optical, are characterized by their diameter or, in other words, form factor. The most widely used are magnetic disks with a form factor of 3.5" (89 mm) and optical disks with a form factor of 5.25" (133 mm).

Information on the MD is written and read by magnetic heads along concentric circles - tracks. The number of tracks on an MD and their information capacity depend on the type of MD, the design of the MD drive, the quality of the magnetic heads and the magnetic coating.

Each MD track is divided into sectors. One track sector can hold 128, 256, 512, or 1024 bytes, but typically 512 bytes of data. Data exchange between the NMD and RAM is carried out sequentially by an integer number of sectors. A cluster is a minimal unit of information placement on a disk, consisting of one or more adjacent track sectors.

When writing and reading information, the MD rotates around its axis, and the magnetic head control mechanism brings it to the track selected for writing or reading information.

Data on disks is stored in files, which are usually identified with a section (area, field) of memory on these storage media.

File is a named area of ​​external memory allocated to store the given array.

The memory field for the created file is allocated as a multiple of a certain number of clusters. Clusters allocated to one file can be located in any free disk space and are not necessarily adjacent. Files stored in clusters scattered across the disk are called fragmented.

For packages of magnetic disks (disks installed on the same axis) and for double-sided disks, the concept of “cylinder” is introduced. A cylinder is a set of MD tracks located at the same distance from its center.

4.2. Floppy disk drives

On a flexible magnetic disk (floppy disk), a magnetic layer is applied to a flexible base. The HDDs used in modern PCs have a 3.5" form factor; they are placed in a hard plastic cassette to protect them from dust and mechanical damage. The write prohibition mode on these floppy disks is set by a special switch located in the lower left corner of the floppy disk.

Each new floppy disk should be formatted before working with it. Formatting a floppy disk is the creation of a structure for recording information on its surface: marking tracks, sectors, recording markers and other service information.

Basic rules for handling floppy disks:

do not bend the floppy disk;

do not touch the magnetic coating of the disk with your hands;

Do not expose the floppy disk to magnetic fields;

you need to store the floppy disk at a positive temperature;

you need to remove the floppy disk before turning off the PC;

Insert a floppy disk into and remove it from the drive only when the drive-on indicator light is off.

Communication, communication, radio electronics and digital devices

The domains of magnetic materials used in longitudinal recording are located parallel to the surface of the media. This effect is used when recording digital data by the magnetic field of the head changing in accordance with the information signal. Attempts to increase the surface recording density by reducing the particle size will increase the ratio of the size of the uncertainty zone to the size of the useful zone, not in favor of the latter, and will ultimately inevitably lead to the so-called superparamagnetic effect when the particles go into a single-domain...

Magnetic disk recording technologies

Longitudinal recording

The first examples of hard drives, which appeared in the 70s of the twentieth century, used longitudinal information recording technology. To do this, the surface of the disk, as well as the surface of the magnetic tape, was covered with a layer of chromium dioxide CrO2 or iron oxide, which provides longitudinal magnetization of the recording layer. The coercive force of such a carrier H c = 28 kA/m.

The technology for applying the oxide layer is quite complex. First, a suspension of a mixture of iron oxide powder and molten polymer is sprayed onto the surface of a rapidly rotating aluminum disk. Due to the action of centrifugal forces, it is evenly distributed over the surface of the disk from its center to the outer edge. After polymerization of the solution, the surface is ground and another layer of pure polymer is applied to it, which has sufficient strength and a low coefficient of friction. Then the disc is finally polished. Disks of this type of drive are brown or yellow.

As is known, magnetic materials have a domain structure, i.e. consist of separate microscopic areas - domains , inside which the magnetic moments of all atoms are directed in one direction. As a result, each such domain has a fairly large total magnetic moment. The domains of magnetic materials used in longitudinal recording are located parallel to the surface of the media. If the magnetic material is not affected by an external magnetic field, the orientation of the magnetic moments of individual domains is chaotic and any direction is equally probable. If such material is placed in an external magnetic field, then the magnetic moments of the domains will tend to orient themselves in a direction coinciding with the direction of the external magnetic field. This effect is used when recording digital data by the magnetic field of the head, which changes in accordance with the information signal.

The minimum element (cell) of the memory of the magnetic recording layer, capable of storing one bit of information, is not a separate domain, but a particle (region) consisting of several dozen domains (70-100). If the direction of the total magnetic moment of such a particle coincides with the direction of movement of the magnetic head, then its state can be compared to the logical “0” of the data, if the directions are opposite, to the logical “1”.

However, if neighboring regions have opposite directions of magnetic moments, then the domains located on the boundary between them and touching like poles will repel each other and eventually change the directions of their magnetic moments in some unpredictable way in order to take an energetically more stable position . As a result, an uncertainty zone is formed at the border of the two areas, reducing the size of the area storing a bit of recorded information and, accordingly, the level of the useful signal when reading (Fig. 5.6). The noise level, of course, increases.

Attempts to increase the surface recording density by reducing particle sizes will increase the ratio of the size of the uncertainty zone to the size of the useful zone, not in favor of the latter and, in the end, will inevitably lead to the so-calledsuperparamagnetic effect, when the particles go intosingle-domain stateand will no longer be able to record the recorded information, since neighboring domains with oppositely directed magnetic moments will change their orientation immediately after removing the magnetic field of the recording head. The recording layer material will become uniformly magnetized throughout the entire volume.

Thus, due to the presence of superparamagnetism, longitudinal recording technology, having reached by the middle of the first decade XXI century recording density of 120 Gbit per inch 2 , has practically exhausted its capabilities and is no longer able to provide a significant increase in the capacity of hard drives. This forced developers to turn to other technologies that were free from this drawback.

Perpendicular recording

The possibility of perpendicular recording is based on the fact that in thin films containing cobalt, platinum and some other substances, the atoms of these substances tend to be oriented in such a way that their magnetic axes are perpendicular to the surface of the carrier. Domains formed from such atoms are also located perpendicular to the surface of the carrier.

A signal in the magnetic reading head is formed only when it crosses the magnetic field lines of the domain, i.e. in the place where these lines of force are perpendicular to the surface of the carrier. For a domain located parallel to the surface of the carrier, the magnetic field lines are perpendicular to the surface only at its ends, where they reach the surface (Fig. 5.7a). When the head moves parallel to the domain and, therefore, parallel to its field lines, there is no signal in it. Reducing the domain length in an effort to increase the recording density is only possible to certain limits - until the superparamagnetic effect begins to take effect. If the domains are located perpendicular to the surface of the carrier, then the lines of force of their magnetic fields will always be perpendicular to the surface and will contain information (Fig. 5.7b). There will be no “idle” runs due to the length of the domain. Just as there will be no superparamagnetism, since domains with opposite magnetization will not repel each other. It is obvious that the recording density on a medium with perpendicular magnetization can be obtained higher.

A disc designed for perpendicular recording requires special manufacturing technology. The base of the plate is carefully polished, and then a leveling layer of nickel phosphate is applied to its surface using a vacuum deposition method. NiP thickness of the order of 10 microns, which, firstly, reduces surface roughness, and secondly, increases adhesion to subsequent layers (Fig. 5.8).

Next, a layer of soft magnetic material is applied, which makes it possible to read data from the recording layer, and the recording layer itself is made of a material with perpendicular orientation of the magnetic domains. Cobalt (Co), platinum ( Pt), palladium (Pd ), their alloys with each other and with chromium ( Cr ), as well as multilayer structures consisting of thin films of these metals several atoms thick.

Apply on top of the recording layer protective film made of glass ceramics, with a thickness of the order of hundredths of a micron.

Recording information on a recording layer with perpendicular magnetization has its own characteristics. In order to ensure an acceptable signal level and ensure a good signal-to-noise ratio, the magnetic field lines generated by the recording head must, passing through the recording layer, close again to the head core. This is what the soft magnetic sublayer located below the recording layer serves for this purpose (Fig. 5.9).

According to preliminary forecasts of experts, perpendicular recording technology will allow recording densities of up to 500 Gbit/inch 2 . In this case, the capacity of a 3.5-inch drive will be 2 TB, a 2.5-inch drive will be 640 GB, and a 1-inch drive will be 50 GB. However, these are only preliminary forecasts. It is possible that the upper limit will be 1 Tbit/inch 2 and even more. The future will tell.

Promising magnetic recording technologies

Perpendicular recording technology is currently under active development and is still far from reaching its maximum recording density. However, this moment will come someday. Maybe even sooner than it seems now. Therefore, research in the search for new highly efficient magnetic recording technologies is already underway.

One such technology is thermomagnetic recordingHAMR (Heat Assisted Magnetic Recording), i.e. recording with media preheating. This method involves short-term (1 picosecond) heating of the area of ​​the recording medium with a focused laser beam - the same as in magneto-optical recording.The difference between technologies is manifested in the way information is read from disk. In magneto-optical drives, information is read by a laser beam operating at a lower power than when recording, and with thermomagnetic recording, information is read by a magnetic head in the same way as from a regular hard drive.And the recording density here is planned to be much higher than in magneto-optical formats MD, CD - MO or DVD - MO - up to 10 Tbit/inch 2 . Therefore, other materials are needed as a recording medium. Currently, such materials are considered various connections platinum, cobalt, neodymium, samarium and some other elements: Fe 14 Nd 2 B, CoPt, FePt, Co 5 Sm, etc. Such materials are very expensive - both because of the high cost of the rare earth elements included in their composition, and because of the complexity and high cost technological process upon their preparation and application to the surface of the intended carrier base. Write/read head design in technology HAMR it is also assumed to be completely different than in magneto-optical recording: the laser should be located on the same side as the magnetic head, and not on the opposite side, as in magneto-optical recorders (Fig. 5.10). Heating is supposed to be carried out to a temperature of about 100 degrees Celsius, not 180.

Another promising direction in the development of magnetic recording is the use as a recording layer of materials in which the particles are arranged in a clearly structured domain array ( Bit Patterned Media ). With this structure, each bit of information will be stored in just one cell-domain, and not in an array of 70-100 domains (Fig. 5.11).

Such a material can either be created artificially using photolithography (Fig. 5.12), or an alloy with a suitable self-organizing structure can be found.

The first method is unlikely to be developed, since to obtain material allowing a recording density of at least 1 Tbit/inch 2 , the size of one particle should be a maximum of 12.5 nm. Neither the existing nor the lithography technology planned for the next 10 years provides this. Although there are quite clever solutions that allow you not to discount this approach.

Search for self-organizing magnetic materials (SOMA - Self-Ordered Magnetic Array) very promising direction. For several years now, Seagate specialists have been pointing out the properties of the FePt alloy evaporated in a hexane solvent. The resulting material has a perfectly smooth cellular structure. The size of one cell is 2.4 nm. If we take into account that each domain has high stability, we can talk about the acceptable recording density at the level of 40-50 Tbit/inch 2 ! This appears to be the final limit for recording on magnetic media.

S

Zones of uncertainty

Rice. 5.6. Zones of uncertainty arising from longitudinal recording

There is a signal

No signal

Rice. 5.7. Media with parallel(s)

and perpendicular (b) magnetization

Sublayer of soft magnetic material

Disc base (Al)

Leveling layer ( NiP)

Recording layer with perpendicular magnetization

Protective layer

Rice. 5.8. Hard disk structure with perpendicular

magnetization

Hard magnetic recording layer

Soft magnetic sublayer

Rice. 5.9. Recording on material with perpendicular

magnetization

Recording pole

Return pole pole

Rice. 5.10. Magneto-optical head HARM

Rice. 5.11. BRM microstructure: 1 - area corresponding to one bit of information during normal recording; 2 - an array whose boundaries coincide with the boundaries of the domains; 3 - domain that is capable of storing one bit of data

Rice. 5.12. Recording layer obtained using photolithography