Physically external drive no different from internal. It can also store data, has a set of disks, heads and controllers. But, unlike its stationary counterpart, which is constantly imprisoned inside system block, a removable drive is clad in a case, the style and design of which may be different. It is both aesthetic and protective. Before damaging the bare parts of the disk, you first have to go through the case. The media is usually connected via USB, which gives it general versatility, because today it is difficult to find a PC or laptop without this connector.

Advantages and disadvantages

The main plus of removable media is its mobility and the ability to use it as a giant flash drive. This advantage was especially appreciated by people working in an IT environment when you need to boot from another drive at the customer's or quickly install some required software. The advantages include a more interesting appearance, which is often a masterpiece of art.

Among the shortcomings, one can single out the increased fragility of hard drives in general. Sometimes a light blow is enough for the head to fall on the disk and not be able to start again. Despite the fact that new SSDs can withstand much greater shocks, shocks are also fatal for them, since some of the elements on the board can simply break off.

Another significant disadvantage can be considered a slow speed, if we talk specifically about hard disk drives. Like it or not, but the rate of charge transition from one state to another in new SSD will always be an order of magnitude higher than the speed of spinning up the disk and positioning the magnetic head on it.

Why you need an external drive

The range of use of removable drives is quite wide. Everyone can use it differently. Someone transfers work files from one PC to another, someone backs up the system, and someone just uses their drive for storage a large number films. For IT people, a hard drive can be an additional tool. After all, from such a drive you can easily boot on any PC and carry out diagnostics or install software. And if you take into account large volume, then you can create a multi-boot drive that contains tools for all occasions, from reinstalling Windows before the treatment of a regular hard drive.

Types of external memory drives

It is now possible to divide all external memory drives into two large types:

• solid state drives;
• hard disk drive.

It is worth saying right away that there is also a hybrid that uses both approaches, but about it separately.

A hard disk drive typically contains 1 to 4 physical magnetic disks. Sequences are recorded on them using magnetic heads, which are then converted into human-readable data. The magnetic head can move from the beginning of the disk to its edge, or vice versa, positioning itself on a certain area to search or write data. The disk itself rotates at a speed of approximately 5400 rpm. There are also faster models, reaching up to 10,000 rpm. The weak point of the hard drive is small files, for reading which the head has to constantly change its position. And if you take into account fragmentation, due to frequent writing and reading to the hard disk, then reading even one small file can take precious milliseconds. All work to ensure the smooth operation of the disk drive, magnetic head and positioning system is taken over by the electronics unit. located on the body of the device.

A hard drive may have a small cache, a small block of memory of about 32 or 64 MB. It is needed for preliminary storage of data being written or read, increasing the speed of reading, and also so that once again you do not need to access the drives directly. In new hybrid models, a small . The noise that a person hears when a hard disk drive is working is emitted by a spinning spindle and a positioning device.

Now a little about SSD. It has no moving parts or heads. The entire mechanism for reading and writing data is completely built on microcircuits, like a flash drive. And, in fact, the type of memory is used from there. Without going into technical details, as a result of the applied signal, a charge is formed in certain cells, which represents one bit of information. By checking the number of charges and empty spaces, the drive makes up a set of bits, which then form more human-readable data, such as pictures, videos or music. A significant drawback of SSDs, and flash drives too, is the too small resource of read-write-rewrite cycles. But the speed of action is simply amazing.

Specifications of external drives

Like all complex electronic devices, external hard drives contain a bunch of various characteristics and parameters. Let's see what you need to pay attention to first of all.

Form factor and interface

Form factor refers to the size and design of the device. External hard drives today can be found in 3 different configurations: 1.8'', 2.5'', 3.5''.

3.5 inches is the largest external hard drive known. Such models almost always come with network adapter to provide separate power. 2.5 inches is the most common form factor that does not require additional power and can receive it via USB.

1.8 inches - mainly used for SSD. As for interfaces, USB is now installed on all modern external hard drives, displacing other outdated standards.

Memory type and size

These two indicators significantly affect the cost of the device. At the same time, the run-up between SSD and HDD is quite noticeable. For comparison, a 500 GB SSD external hard drive has a price of 10,000 rubles. But the classic HDD with the same volume can be bought for 2,800 rubles. As you can see, the difference is big. But if you remember the history, the first hard drives also cost like cars, and then gradually became cheaper and more affordable. Perhaps the same thing will happen with the SSD, you just need to wait a bit.

Now a little about the differences between these two types of media. An SSD writes and reads data faster than an HDD. And a lot. Many users note that the speed of loading the operating system on the SSD has increased several times. But HDD is more reliable in terms of data safety. It is unlimited in the number of write-rewrite cycles. The failure is mainly affected by the timely wear of the mechanical parts, as well as the start and stop of the drive. It is worth noting that recent developments in SSDs have also made it possible to increase their service life. Therefore, it is possible that in the near future, solid state drives will be able to completely replace the HDD.

Everything, as always, determines the budget. Before choosing a reliable hard drive, you need to weigh the pros and cons. If the budget is solid, then you can safely turn your eyes towards the SSD. And do not be afraid of excessively rapid failure. After all, an external hard drive, as a rule, is used from time to time. That is, the number of write-rewrite cycles will not grow at the same rate as when using it as a system one. And for storing images of various systems on it for the purpose of subsequent installation from it, this is generally good. After all, the data from the media will only be read. Having decided which external hard drive is better to buy, take a look at the manufacturer's official website - there are often useful information or software.

To store large quantities SSD data hardly suitable, since each extra gigabyte will cost a pretty penny. But the outer hard HDD disk for 4 TB can be purchased for 20,000 rubles. This volume is enough to burn approximately 2800 DVDRip movies.

Manufacturers Overview

Who only does not make hard disks. Both external and internal. But still there are a few of the best that keep the brand for many years:

• Toshiba. A Japanese company that was one of the first to manufacture magnetic disk drives. Now on the market you can find many interesting models from this company;
• Saegate. Probably the only company that started in 1985 with the production of discs and is still doing this. Manufactures both HDD and SSD;
• western digital. Another American company that specializes in the production of drives. It has an interesting color gradation of its product lines;
• Samsung. Well, this company makes just about everything, including hard drives. Like the rest of the products, Samsung's carriers are also not bad.

The best models of external hard drives, according to the editors

Western Digital My Passport 2 TB (WDBUAX0020B)

The attractive appearance of this 2 TB external hard drive, as well as its speed characteristic of 500 Mb / s, are estimated at 4,000 rubles. The disk form factor is the popular 2.5-inch. You can connect it using USB-version 3.0. And here's what users say about it.

Western Digital My Passport 2 TB

Toshiba Canvio Ready 1TB

External hard drive 1 TB, made in two color styles: completely white and black. Disc rotation speed 5400 rpm. The declared external data transfer rate is 500 Mb/s. The most popular form factor is 2.5 inches. You can buy a removable hard drive for 3,000 rubles.

Toshiba Canvio Ready

Seagate STEB2000200

The model, of course, does not shine with design, but it has several coloring options Samsung knows how to make stylish and at the same time functional gadgets

External hard drive 250 GB type SSD. Made in the most compact form factor - 1.8 inches. The declared data transfer rate is 540 Mb/s. This external SSD hard drive is not the cheapest, you will have to pay 7,100 rubles for it.

Samsung Portable SSD T5

What to do if the computer does not see a removable hard drive

The very first thing to try in this case is to try another connector. By the way, the method is universal and suitable for all devices. And even if another gadget worked fine on this port, it is not a fact that the current device will work here.

If it does not help, you need to look in the device manager and make sure that the problem is not in the drivers. If the gadget is recognized by the system, but there are not enough drivers, then something like “Unknown device” will be written in the manager in the USB block, or just the name of the disk. In theory, drivers on new systems are installed automatically. If this does not happen, then you should try to disable-enable the device from the port and also switch to another port.

If the device is new, then the drive may not be formatted, and it does not even have a partition on it. In order to create a partition and start working, you need to go to the "Control Panel", find the "Administration" section. Select "Computer Management" and then "Disk Management" from the list. All disks that are connected to the system should be displayed here. If our problematic drive is here, then you should try changing its letter with context menu. If there is a disk, but “Not allocated” is written in its area, then this means that there is no partition at all. You can also create it through the context menu.

Removable hard drive repair - nuances

Unfortunately, the only repair that the user can perform at home is ? this full formatting. If the hard drive fails due to bad sectors, then they will be discarded during formatting, leaving only working ones. If the problem is more serious, for example, the head is stuck or the controller is out of order, then without professional help not enough here. It remains only to give a few recommendations for proper handling:

• the hard drive does not tolerate overheating, so you should be careful about the conditions in which the drive is forced to work;
• avoid bumps and falls of the device, even if it is an SSD;
• first sign of instability HDD work- crunching and unusual sounds. In order not to lose data, you need to urgently do them backup on another medium. As for the SSD, no one is insured here at all, it can fail at any second;
• in general, you need to be careful with your electronic friend.

A personal collection of digital data tends to grow exponentially over time. Over the years, the amount of data in the form of thousands of songs, films, photographs, documents, all kinds of video courses is constantly growing and, of course, they must be stored somewhere. computer or, no matter how big it is, it will still someday completely run out of free space.

The obvious solution to the problem of lack of storage space is to buy DVDs, USB flash drives or external hard disk(HDD). Flash drives usually provide several GB of disk space, but they are definitely not suitable for long-term storage, and their price-to-volume ratio is, to put it mildly, not the best. DVDs are a good option in terms of price, but not convenient in terms of burning, rewriting and deleting unnecessary data, but they are slowly dying out and becoming obsolete technology. The external HDD provides a large amount of space, portable, convenient to use, great for long-term data storage.

When buying an external HDD to make right choice, you need to know what to look for first. In this article, we will tell you what criteria should be followed when choosing and buying an external hard drive.

What to look for when buying an external hard drive

Let's start by choosing a brand, the best ones are Maxtor, Seagate, Iomega, LaCie, Toshiba And Western Digital l.
Most important characteristics that you need to pay attention to when buying:

Capacity

The amount of disk space is the first thing to consider. The main rule that you should be guided by when buying is the capacity that you need, multiply by three. For example, if you think that 250 GB of additional hard drive space is enough, buy a model from 750 GB. Drives with large amounts of storage tend to be quite bulky, which affects their mobility, and should also be taken into account by those who often carry an external drive with them. For desktop computers, models with several terabytes of disk space are available for sale.

Form Factor

The form factor determines the size of the device. Currently, 2.5 and 3.5 form factors are used for external HDDs.
2.5-form factors (size in inches) - smaller, lighter, port-powered, compact, mobile.
3.5 form factors - larger in size, have extra food from the mains, are quite heavy (often more than 1 kg), have a large amount of disk space. Pay attention to the mains power supply, because. if you plan to connect the device to a weak laptop, then it may not be able to spin up the disk - and the disk simply will not work.

Rotation speed (RPM)

Second an important factor The one to consider is the rotational speed of the disk, indicated in RPM (revolutions per minute). High speed provides fast data reading and high speed records. Any HDD with a disk rotation speed of 7200 RPM or more is good choice. If speed is not critical for you, then you can choose a model with 5400 RPM, they are quieter and less heated.

Cache size

Every external HDD has a buffer or cache in which data is temporarily stored before it goes to disk. Drives with large caches transfer data faster than those with smaller caches. Choose a model that has at least 16 MB of cache, preferably more.

Interface

In addition to the above factors, another important feature is the type of interface used for data transfer. The most common is USB 2.0. USB 3.0 is gaining popularity, the new generation has significantly increased data transfer speed, models with FireWire and eSATA interfaces are also available. We recommend that you opt for USB 3.0 and eSATA models with high data transfer rates, provided that your computer is equipped with the appropriate ports. If the ability to connect is critical to you external hard drive to possibly more devices - choose a model with a version of the USB 2.0 interface.

Personal computer: external memory

External memory is a memory implemented in the form of external, relative to the motherboard, devices with different principles of information storage and media types, designed for long-term storage information. In particular, all computer software is stored in external memory. External memory devices can be placed both in the computer system unit and in separate cases. Physically, external memory is implemented in the form of drives. Drives are storage devices designed for long-term (which does not depend on power supply) storage of large amounts of information. The storage capacity is hundreds of times greater than the capacity random access memory or generally unlimited when it comes to drives with removable media.

The drive can be considered as a combination of the carrier and the corresponding drive. There are drives with removable and permanent media. A drive is a combination of a read-write mechanism with the corresponding electronic circuits management. Its design is determined by the principle of operation and the type of carrier. The media is the physical medium for storing information. appearance can be disk or tape. According to the principle of storage, magnetic, optical and magneto-optical media are distinguished. Tape media can only be magnetic; disk media uses magnetic, magneto-optical and optical methods of writing and reading information.

The most common are magnetic disk drives, which are divided into hard disk drives (HDD) and floppy disk drives (FFD), and drives on optical discs, such as CD-ROM, CD-R, CD-RW, and DVD-ROM drives.

Hard Disk Drives (HDD)

The HDD is the main device for long-term storage of large amounts of data and programs. Other names: hard drive, hard drive, HDD (Hard Disk Drive). Externally, the hard drive is a flat, hermetically sealed box, inside of which there are several hard round aluminum or glass plates on a common axis. The surface of any of the disks is covered with a thin ferromagnetic layer (a substance that reacts to an external magnetic field), in fact, the recorded data is stored on it. In this case, the recording is carried out on both surfaces of each plate (except for the outer ones) using a block of special magnetic heads. Each head is above the working surface of the disk at a distance of 0.5-0.13 microns. The disk pack rotates continuously and at a high frequency (4500-10000 rpm), so mechanical contact between the heads and disks is unacceptable.

Recording data in the hard disk is carried out as follows. When the strength of the current passing through the head changes, the intensity of the dynamic magnetic field in the gap between the surface and the head changes, which leads to a change in the stationary magnetic field of the ferromagnetic parts of the disk coating. The read operation occurs in reverse order. The magnetized particles of the ferromagnetic coating are the cause of the electromotive force of self-induction of the magnetic head. The electromagnetic signals that arise in this case are amplified and transmitted for processing.

The work of the hard drive is controlled by a special hardware-logical device - the hard disk controller. In the past, this was a separate daughter card that was connected via slots to motherboard. IN modern computers The functions of the hard disk controller are performed by special microcircuits located in the chipset.

A drive can have up to ten disks. Their surface is divided into circles, which are called tracks (track). Each track has its own number. Tracks with the same number, located one above the other on different disks form a cylinder. The tracks on the disc are divided into sectors (numbering starts from one). Sector occupies 571 bytes: 512 allocated for writing necessary information, the rest under the heading (prefix), which determines the beginning and number of the section and the end (suffix), where the check sum, needed to check the integrity of the stored data. Sectors and tracks are formed during disk formatting. Formatting is performed by the user using special programs. No information can be written to an unformatted disc. A hard drive can be divided into logical drives. This is convenient because having multiple logical drives makes it easier to structure the data stored on the hard drive.

There is a huge amount different models hard drives from many companies such as Seagate, Maxtor, Quantum, Fujitsu, etc. To ensure the compatibility of hard drives, standards have been developed for their characteristics, which determine the range of connecting conductors, their placement in adapter connectors, and the electrical parameters of signals. Common are the IDE (Integrated Drive Electronics) or ATA interface standards and the more productive EIDE (Enhanced IDE) and SCSI (Small Computer System Interface). Characteristics of the interfaces through which hard drives are connected to motherboard, largely determine the performance of modern hard drives.

Among other parameters that affect the performance of the HDD, the following should be noted:

• disk circulation speed - nowadays EIDE drives are produced with a rotation frequency of 4500-7200 rpm, and SCSI drives - 7500-10000 rpm;
• cache memory capacity - all modern disk drives have a cache buffer that speeds up data exchange; the larger its capacity, the higher the probability that the cache will contain the necessary information that does not need to be read from disk (this process is thousands of times slower); cache buffer capacity in different devices can vary from 64 KB to 2 MB;
• mean access time - the time (in milliseconds) during which the block of heads is shifted from one cylinder to another. Depends on actuator design and is approximately 10-13 milliseconds;
• the delay time is the time from the moment the head block is positioned on the desired cylinder to the positioning of a specific head on a specific sector, in other words, this is the search time for the desired sector;
• exchange rate - determines the amount of data that can be transferred from the drive to the microprocessor and to reverse direction for certain periods of time; the maximum value of this parameter is equal to the bandwidth of the disk interface and depends on which mode is used: PIO or DMA; in PIO mode, data exchange between the disk and the controller occurs with direct participation CPU, the larger the PIO mode number, the higher the exchange rate; work in DMA mode (Direct Memory Access) allows you to transfer data directly to RAM without the participation of the processor; data transfer speed in modern hard drives ranges from 30-60 MB / s.

Floppy disk drives (FDD)

floppy drive or floppy drive is built into the system unit. Flexible media for NGMD are produced in the form of floppy disks (another name is floppy disk). Actually, the carrier is a flat disc with a special, fairly dense film coated with a ferromagnetic layer and placed in a protective envelope with a movable shutter at the top. Floppy disks are used mainly for the rapid transfer of small amounts of information from one computer to another. Data recorded on a floppy disk can be protected from being erased or overwritten. To do this, you need to move the small protective latch at the bottom of the floppy disk so that an open window is formed. In order to enable recording, this slide must be moved back and the window closed.

The front panel of the drive is displayed on the front panel of the system unit, it has a pocket closed with a shutter, where a floppy disk is inserted, a button for removing the diskette and an indicator light. The floppy disk is inserted into the disk drive with the top latch forward, it must be inserted into the drive pocket and smoothly pushed forward until it clicks. The correct insertion direction of the floppy disk is marked with an arrow on the plastic case. To remove a floppy disk from the drive, you need to press its button. The light indicator on the drive indicates that the device is busy (if the light is on, it is not recommended to remove the floppy disk). Unlike a hard disk, a floppy disk drives only when a read or write command is given; at other times, it is at rest. The read-write head during operation mechanically contacts the surface of the floppy disk, which leads to rapid wear of the floppy disk.

As in the case of a hard disk, the surface of a floppy disk is divided into tracks, which in turn are divided into sectors. Sectors and tracks are obtained when a floppy disk is formatted. The floppy disks are now shipped formatted.

The main parameters of a floppy disk are the technological size (in inches), recording density and total capacity. The sizes distinguish between 3.5-inch floppy disks and 5.25-inch floppy disks (now no longer used). Recording density can be simple SD (Single Density), double DD (Double Density) and high HD (High Density). The standard capacity of a 3.5-inch floppy disk is 1.44 MB, 720 KB floppy disks can be used. 3.5-inch high-density HD floppy disks with a capacity of 1.44 MB are now the standard.

When using a floppy disk, you should adhere to the following rules:

• do not touch the working surface of the diskette;
• do not bend the disk;
• do not remove the metal shutter, a dirty floppy disk can damage the heads;
• keep floppy disks away from the source of magnetic fields;
• before use, check the diskette for viruses using an anti-virus program.

Optical drives

CD-ROM drive

Starting from 1995 in the basic configuration personal computer instead of 5.25-inch drives, they began to include a CD-ROM drive. The abbreviation CD-ROM stands for Compact Disk Read Only Memory. The principle of operation of this device is to read digital data using a laser beam that is reflected from the surface of the disk. An ordinary CD is used as a storage medium. Digital recording on a CD differs from recording on magnetic discs in high density, so a standard CD has a capacity of about 650-700 MB. Such large volumes are typical for multimedia information (graphics, music, video), so CD-ROM drives refer to media hardware. In addition to multimedia publications (electronic books, encyclopedias, music albums, videos, computer games) a variety of system and application software is distributed on CDs. software large volumes (operating systems, office suites, programming systems, etc.)

Compact discs are made of transparent plastic with a diameter of 120 mm. and 1.2 mm thick. A layer of aluminum or gold is sprayed onto the plastic surface. In conditions of mass production, information is recorded on a disc by extrusion on the surface of the track, in the form of a series of depressions. This approach provides a binary record of information. Deepening (pit - pit), surface (land - land). A logical zero can be represented by either a pit or a land. The logical unit is encoded by the transition between the pit and the land. From the center to the edge of the CD, a single track is applied in the form of a spiral 4 microns wide with a 1.4 micron pitch. The disk surface is divided into three regions. The initial (Lead-In) is located in the center of the disk and is read first. It contains the contents of the disk, the address table of all entries, the label of the disk, and other service information. The middle area contains basic information and occupies most of the disk. The end area (Lead-Out) contains the end-of-disk marker.

For stamping, there is a special prototype matrix (master disk) of the future disk, which extrudes tracks on the surface. After stamping, the surface of the disc is applied protective film from transparent varnish.

The CD-ROM drive contains:

• an electric motor that rotates the disk;
• an optical system consisting of a laser emitter, optical lenses and sensors and designed to read information from the disk surface;
• a microprocessor that manages the mechanics of the drive, the optical system and decodes the read information into a binary code.
• The CD is spun by an electric motor. A beam from a laser emitter is focused onto the surface of the disk using the drive of the optical system. The beam is reflected from the disk surface and fed through the prism to the sensor. The luminous flux is converted into an electrical signal, which enters the microprocessor, where it is analyzed and converted into a binary code.

Key Features of CD-ROM:

• data transfer rate - measured in multiples of the speed of an audio CD player (150 Kbytes / sec) and characterizes the maximum speed at which the drive transfers data to the computer's RAM, for example, a 2-speed CD-ROM (2x CD-ROM) will read data at 300 KB/s, 50-speed (50x) - 7500 KB/s;
• access time - the time required to search for information on the disk, measured in milliseconds.
• The main disadvantage of standard CD-ROMs is the inability to write data, but CD-R write-once and CD-RW rewrite devices exist.

CD-R drive (CD-Recordable)

Outwardly similar to CD-ROM drives and compatible with them in terms of disc sizes and recording formats. Allows you to perform a one-time write and an unlimited number of reads. Data recording is carried out using special software. Recording speed of modern CD-R drives is 4x-8x.

CD-RW drive (CD-ReWritable)

They are used for multiple recording of data, and you can either simply add new information to free space, or completely overwrite the disk with new information (previous data is destroyed). As with CD-R drives, in order to write data, you must install special programs, and the recording format is compatible with conventional CD-ROM. The write speed of modern CD-RW drives is 2x-4x.

Storage deviceDVD (Digital Video Disk)

Digital video reader. Externally, a DVD-ROM is similar to a regular CD-ROM (diameter - 120 mm, thickness 1.2 mm), but differs from it in that up to 4.7 GB can be recorded on one side of the DVD-ROM, and up to 9.4 GB. In the case of using a two-layer recording scheme, up to 8.5 GB of information can already be placed on one side, respectively, on two sides - about 17 GB. DVDs can be overwritten.

The most important factor hindering the widespread use of CD-R, CD-RW and DVD drives is the high cost of both themselves and removable media.

test questions

What is external memory? What types of external memory do you know?

What is a hard drive? What is it for? What is the capacity of modern hard drives?

How are read and write operations performed on the hard drive?

What is the operation of formatting magnetic disks?

What are the types of standard disk interfaces?

What parameters affect the performance of a hard drive? How?

What is a floppy disk? What are the similarities and differences between it and a hard drive?

What rules should be followed when using a floppy disk?

What types of optical disc drives do you know? How do they differ from each other?

How is information read from CDs?

How is data transfer rate measured in optical media drives?

An easy way to speed up your computer is to install an SSD drive on it. We have already talked about it in one of the previous articles. These drives come in several types, and I would like to devote today's article to just that. First - SATA solid state drive, it usually comes in a 2.5" form factor and is a versatile solution with very good speed and a fairly reasonable price.

It is suitable for any computer, for almost any laptop (there are exceptions, such as SONY models, which use a 1.8 "form factor disk). Next on the list we have PCI, especially pay attention to PCI 3.0 SSDs - they simply crazy speed and you might be surprised at the performance you get with these drives.

But, like all good things, they have one drawback - a rather high price, which is often 2 or even 3 times higher than conventional SATA 2.5 SSD drives. There are also mSATA (in the picture below), which is short for "mini SATA", they are most often used in laptops, however, in terms of speed, such drives are no different from conventional SATA 2, that is, it is the same, but in a smaller form -factor.

See how much smaller the mSATA SSD is (green printed circuit board top) compared to conventional 2.5" HDD

It is noteworthy that there are SSDs exclusively for Apple (they have remained separate “personalities” here too), and they are even more expensive, although they do not differ in performance from the same PCI SSDs. The write speed here can be 700 Mb / s - which is a chic indicator.

If you want to buy an SSD for yourself, then in any case you will have to choose between SATA and PCI versions, and there is already a question of price. If you spend a lot of time at your computer, be sure to try the PCI version of the drive. Because it itself goes into a RAID array (this is when 2 hard drives are connected into one, roughly speaking), in this case, information is read from two devices at once, which speeds up the system by exactly 2 times.

PCI SSD - installed inside the computer system unit

That is, for example, the same Windows is installed immediately on 2 flash drives (2 different chips) and read from them at the same time, which is a truly great solution for increasing computer performance, I definitely recommend buying it.

If you just want to somehow speed up your old computer, which, perhaps, you plan to change to something more productive soon, or just want to try a solid-state drive for the first time in work - I definitely recommend taking everyone familiar and time-tested SATA 2.5 SSD.

Storage media (floppy disks, hard disks, CD-ROMs, magneto-optical disks, etc.) and their main characteristics.

External (long-term) memory is a place for long-term storage of data (programs, calculation results, texts, etc.) that are not used in this moment in computer memory. External memory, unlike operational memory, is non-volatile. External memory media, in addition, provide data transportation in cases where computers are not networked (local or global).

To work with external memory, you must have a drive (a device that provides recording and (or) reading information) and a storage device - a carrier.

The main types of drives:

floppy disk drives (FPHD);

hard disk drives (HDD);

magnetic tape drives (NML);

drives CD-ROM, CD-RW, DVD.

They correspond to the main types of media:

floppy disks (Floppy Disk) (3.5'' diameter and 1.44 MB capacity; 5.25'' diameter and 1.2 MB capacity 5.25'', also discontinued)), disks for removable media;

hard magnetic disks (Hard Disk);

cassettes for streamers and other NML;

CD-ROMs, CD-Rs, CD-RWs, DVDs.

Memory devices are usually divided into types and categories in connection with their principles of operation, operational, technical, physical, software and other characteristics. So, for example, according to the principles of functioning, the following types of devices are distinguished: electronic, magnetic, optical and mixed - magneto-optical. Each type of device is organized on the basis of the appropriate technology for storing/reproducing/recording digital information. Therefore, in connection with the type and technical performance of the information carrier, there are: electronic, disk and tape devices.

The main characteristics of drives and media:

information capacity;

speed of information exchange;

reliability of information storage;

price.

Let us dwell in more detail on the consideration of the above drives and media.

The principle of operation of magnetic storage devices is based on methods of storing information using the magnetic properties of materials. As a rule, magnetic storage devices consist of the actual devices for reading / writing information and a magnetic medium, on which the recording is directly carried out and from which information is read. Magnetic storage devices are usually divided into types in connection with the performance, physical and technical characteristics of the information carrier, etc. The most commonly distinguished are: disk and tape devices. The general technology of magnetic storage devices is to magnetize sections of the carrier with an alternating magnetic field and read information encoded as regions of variable magnetization. Disk carriers, as a rule, are magnetized along concentric fields - tracks located along the entire plane of a discoidal rotating carrier. Recording is done in digital code. Magnetization is achieved by creating an alternating magnetic field using the read/write heads. The heads are two or more magnetic controlled circuits with cores, the windings of which are supplied with AC voltage. A change in the voltage value causes a change in the direction of the lines of magnetic induction of the magnetic field and, when the carrier is magnetized, means a change in the value of the information bit from 1 to 0 or from 0 to 1.

Disk devices are divided into flexible (Floppy Disk) and hard (Hard Disk) drives and media. The main property of disk magnetic devices is the recording of information on a carrier on concentric closed tracks using physical and logical digital encoding of information. The flat disc media rotates during the read/write process, which ensures the maintenance of the entire concentric track, reading and writing is carried out using magnetic read/write heads that are positioned along the radius of the media from one track to another.

For the operating system, data on disks is organized into tracks and sectors. Tracks (40 or 80) are narrow concentric rings on the disc. Each track is divided into sections called sectors. When reading or writing, the device always reads or writes an integer number of sectors, regardless of the amount of information requested. The sector size on a floppy disk is 512 bytes. The cylinder is the total number of tracks from which information can be read without moving the heads. Because a floppy disk has only two sides, and a floppy disk drive has only two heads, there are two tracks per cylinder in a floppy disk. A hard drive can have many platters, each with two (or more) heads, so there are many tracks per cylinder. A cluster (or data allocation cell) is the smallest area of ​​a disk that can be operating system uses when writing a file. Usually a cluster is one or more sectors.

The floppy disk must be formatted before use. its logical and physical structure.

Diskettes require careful handling. They may be damaged if

touch the recording surface;

write on the floppy disk label with a pencil or ballpoint pen;

bend a diskette;

overheat the floppy disk (leave it in the sun or near the radiator);

expose the disk to magnetic fields.

Hard disk drives combine media(s) and a read/write device in one package, as well as, often, an interface part called a hard disk controller. A typical design of a hard disk is the execution in the form of a single device - a chamber, inside which there is one or more disk media placed on one axis, and a block of read / write heads with their common drive mechanism. Usually, next to the chamber of media and heads are circuits for controlling heads, disks and, often, an interface part and (or) a controller. The disk device interface itself is located on the interface card of the device, and the controller with its interface is located on the device itself. The drive circuits are connected to the interface adapter using a set of cables.

Operating principle hard drives similar to this principle for the GMD.

The main physical and logical parameters of the railway.

Disc diameter. The most common drives with disk diameters are 2.2, 2.3, 3.14 and 5.25 inches.

Number of surfaces - determines the number of physical disks strung on the axis.

Number of cylinders - determines how many tracks will be located on one surface.

Number of sectors - the total number of sectors on all tracks of all surfaces of the drive.

The number of sectors per track is the total number of sectors per track. For modern drives, the indicator is conditional, because. they have an unequal number of sectors on external and internal tracks, hidden from the system and user by the device interface.

The transition time from one track to another is usually 3.5 to 5 milliseconds, and the fastest models can be from 0.6 to 1 millisecond. This indicator is one of the determinants of the speed of the drive, because. it is the transition from track to track that is the longest process in a series of random read / write processes on a disk device.

Setup time or seek time - the time taken by the device to move the read / write heads to the desired cylinder from an arbitrary position.

The data rate, also called throughput, determines the speed at which data is read from or written to disk after the heads are in position. It is measured in megabytes per second (MBps) or megabits per second (Mbps) and is a characteristic of the controller and interface.

Currently, hard disks with a capacity of 10 GB to 80 GB are mainly used. The most popular are disks with a capacity of 20, 30, 40 GB.

In addition to NGMD and NGMD, removable media are often used. A fairly popular drive is Zip. It is available as built-in or stand-alone units connected to the parallel port. These drives can store 100 and 250 MB of data on 3.5" floppy cartridges, provide access times of 29 ms, and transfer rates up to 1 MB/s. If a device connects to the system through a parallel port, the data rate is limited by the parallel port rate.

To the type of drives on removable hard drives refers to the Jaz drive. The capacity of the used cartridge is 1 or 2 GB. The disadvantage is the high cost of the cartridge. Main application - backup data.

In magnetic tape drives (most often streamers act as such devices), recording is done on mini-cassettes. The capacity of such cassettes is from 40 MB to 13 GB, the data transfer rate is from 2 to 9 MB per minute, the tape length is from 63.5 to 230 m, the number of tracks is from 20 to 144.

CD-ROM is a read-only optical storage medium that can store up to 650 MB of data. Accessing data on a CD-ROM is faster than data on floppy disks, but slower than on hard drives.

A CD with a diameter of 120 mm (about 4.75'') is made of polymer and covered with a metal film. Information is read from this metal film, which is covered with a polymer that protects data from damage. CD-ROM is a one-sided storage medium.

Information is read from the disk by registering changes in the intensity of the low-power laser radiation reflected from the aluminum layer. The receiver or photosensor determines whether the beam is reflected from a smooth surface, scattered or absorbed. Scattering or absorption of the beam occurs in places where indentations were made during the recording process. The photo sensor senses the scattered beam, and this information is fed to a microprocessor in the form of electrical signals, which converts these signals into binary data or sound.