Accumulators and carriers of information.

Information storage - a device that reads and/or writes information.

Information storage devices are:

· internal and external:

· with removable and non-removable storage media;

· stationary and portable.

The internal drives are in system block PC and are connected to special connectors on the motherboard.

External and portable storage is in its own case and connects to the computer through standard input / output ports. External storage devices are used for Reserve copy and storage of information, as well as for transporting data from one computer to another.

Information carrier - this is a device on which information is directly recorded (stored), for example, a disk, a magnetic tape cassette, etc.

The drive and the information carrier can be made in the same housing, i.e. form one whole, for example, a hard disk HDD (Fig. 13).

Rice. 13. Hard Disk Drive HDD

The drive may have removable media, for example:

at the FDD drive removable media - floppy disk floppy disk);

at DVD drive - RW (Fig. 14) removable storage medium - DVD disc.

Rice. 14. DVD-RW drive

In some cases, the division into storage and media is conditional. For example, the internal storage of information is random access memory ( RAM ) and portable storage FLASH A card is both a storage device and a carrier of information.

Main drives and storage media

The main characteristic of a carrier (drive) is its capacity, i.e. maximum volume information that can be recorded on this device. Drive capacity is measured in the following units:

AT recent times floppy disks and CDs - disks are outdated, they will no longer be used in the near future and are being actively replaced by more capacious media FLASH -cards (Fig. 15) and DVD discs.

Rice. 15.. FLASH card

The capacity of the main media (drives).

Good day.

For storing and transferring large amounts of information, it is quite convenient to use external HDs. Many, of course, will object - after all, there are "clouds". But not all information can be stored there (there is confidentiality and everything ...), and the Internet is not everywhere and always fast.

Agree, it’s convenient when you have music, photos, movies, games on an external medium, and when you come to visit, you can quickly connect your disk to your PC and turn on the playback of a pleasant composition ...

In this article I would like to present a few important points(in my opinion), which you should pay attention to when choosing and buying an external drive. Of course, I have never been to a manufacturer of such devices, and nevertheless, I have some experience (): at work I have to deal with three dozen such media, and at home - a dozen more.

👉By the way!

You can buy some models of disks with discounts

7 points when choosing an external HDD

⑴ Storage capacity

The bigger, the better!

This rule is also true for external hard drives (there is never enough space). Today, one of the most popular volumes is 1÷4 TB (and the cheapest in terms of price / number of GB). Therefore, I recommend to look narrowly at disks of this volume.

About disks 5-8 TB and more...

These are also on sale today. But there are a couple of "buts" that I would recommend paying attention to:

• not "run-in" technologies - the reliability of such disks often leaves much to be desired. And in general, I would not recommend immediately grabbing onto any new and large disks (for now, manufacturers will bring their manufacturing technology to perfection ...);
• such disks often need extra food. If you buy a disk for a laptop or other portable gadget (which you want to connect only to a USB port), then such disks will create unnecessary "problems" for you...

⑵ About connection interface

The most popular interfaces currently on sale are USB 2.0 and USB 3.0. I recommend immediately "aiming" and choosing USB 3.0 (up to 5 Gb / s; you will even notice the difference in speed by eye).

In practice, usually, the speed of copying / reading from an external drive via USB 2.0 reaches 30-40 Mb / s, via USB 3.0 - up to 80-120 Mb / s. Those. there is a difference, especially since USB disk 3.0 is universal, and it can be connected even to those devices that only support USB 2.0.

By the way, to distinguish a USB 2.0 port from USB 3.0 - pay attention to the color. Now most manufacturers mark USB ports 3.0 in blue.

How to distinguish a USB 3.0 port from a USB 2.0 port (USB 3.0 port is marked in blue)

By the way if you have a new port on your laptop (computer) USB Type-C(speed up to 10 Gbit / s) - now disks with a similar interface are starting to appear on sale, and it makes sense to take a closer look at such models.

I also note that there are all kinds of adapters for connecting USB 3.0 drives (for example) to the new USB Type-C port.

Addition: There are also other SATA, eSATA, FireWire, Thunderbolt standards. They are much less common than USB and I don’t see the point in dwelling on them, because. the vast majority of users will be satisfied with the USB interface.

⑶ Pro separate power supply

There are drives both with an additional power source and without it (working from USB power supply port). As a rule, drives that work only from a USB port do not exceed 4-5 TB (this is the maximum that I have seen on sale).

I note that drives with an additional adapter work faster and more stable. But, nevertheless, extra wires create inconvenience, and it is not always possible to connect the drive to the outlet - for example, when using the drive while working on a laptop.

There is one more problem to pay attention to.: not always and not all models of disks have enough power from the USB port (for example, in cases where the device is powered by a small netbook or not only the disk is connected to USB - there may not be enough power for the HDD!). In cases of lack of power - the disk may simply become "invisible". I mentioned this in this article:

From practice...

Drives that had enough power from the USB port: Seagate Expansion 1-2 TB (not to be confused with the Portable Slim line), WD Passport Ultra 1-2 TB, Toshiba Canvio 1-2 TB.

Drives that had problems (and sometimes became invisible in Windows): Samsung 1-2 TB, Seagate Portable Slim 1-2 TB, A-DATA 1-2 TB, Transcend StoreJet 1-2 TB.

In principle, if you encounter a lack of power, you can try using a USB hub with a power supply. Such a device will allow you to connect several disks to one USB port at once, and all of them will have enough power (even when connected to a "weak" netbook).

USB hub with power supply

⑷ Pro form factor // size

Form factor - sets the size of the disk. 10-15 years ago - a special class as "External HDD and "was absent, and many used ordinary HDDs installed in a special box (box) - that is, they assembled such a portable disk on their own. From there, the two most popular form factors of external HDDs came out - 2.5 and 3.5 inches.

3,5"

Large, heavy and overall wheels. The most capacious today (the capacity of one HDD reaches 8 TB and more!). Most suitable for a stationary PC (or a laptop that is rarely transferred). As a rule, they provide a higher data transfer rate (compared to 2.5").

Such disks are rarely produced in shock-resistant cases, so they are extremely afraid of shaking or vibrations. Another feature: they cannot work without a power supply (absolutely!). extra wires don't make them feel comfortable...

Stationary external hard 3.5" disk (pay attention to the dimensions) - connects to a 220V network via a power supply

2,5"

The most popular and demanded type of disks. Their dimensions are comparable to a regular smartphone (a little more). Most drives have enough power from the USB port to work properly. Convenient both on the road and at home, for connecting to both a PC and a laptop (and indeed, to any equipment with a USB port).

Often, when such discs are placed in special. a shock-resistant case that allows them to extend their "survivability" (important for disks that are often on the road and are subject to vibrations).

Of the minuses: their capacity is somewhat lower than that of 3.5 "disks (today it reaches 5 TB). Also, some models of disks do not always have enough power from the USB port, and they "fall off" during operation (i.e. become invisible to Windows OS).

⑸ Drive speed

Your disk speed depends on several components:

1. from the interface: today the best option in terms of price / speed ratio is the USB 3.1 standard (USB Type-C is also gaining popularity);
2. on spindle speed: 5400 rpm, 7200 rpm and 4200 rpm are found in external drives. The higher the speed - the higher the speed of reading information (and the more the disk makes noise, and the more it heats up). Usually 2.5 "discs go 4200 and 5400 rpm, 3.5" disks - 7200 rpm;
3. on cache size (temporary memory that allows you to receive fast access to the most frequently used information) : Now the most popular drives with 8-64 MB cache. Naturally, the higher the cache, the more expensive the disk ...

Personal opinion: in most cases, external drives are bought for storage of various multimedia data - music, movies, photos, etc. And with such tasks, the difference in the speed of the disk from 7200 rpm and 5400 rpm is not significant, and does not play a big role.

The only point (in terms of speed) when choosing, I would focus on the presence of a USB 3.1 interface (otherwise there are still quite a few drives with a USB 2.0 interface on sale).

⑹ Protection against moisture and fur. damage. Passwords and hack protection

Some disc models have additional protection against shocks, dust, moisture, etc. Naturally, such discs are more expensive than usual ones, sometimes the cost is several times higher!

In my opinion, all these bells and whistles - if they help, then only from very minor incidents. If the disk is waiting for a strong blow, then the case, although it will soften it, will not help much.

Based on my practice of "sad" cases, I'll say that the shock-resistant case for models whose cost does not exceed $350 did not prevent damage to the disk. I haven’t used more expensive discs, and I can’t criticize in absentia 👀.

In my opinion, if you buy such disks, then the cost is no higher than 10-20% of the cost of other disks (and certainly such protection does not cost like 2-3 ordinary disks).

I will add that often the disks fail and without any shocks and concussions. I would recommend paying more attention to the reliability of the ruler ( model range HDD) and reviews about it.

As for all kinds of password protection of the drive, the drive can also be protected using free utilities(moreover, it is not known what will be more reliable).

👉 To help!

You can find out how in this article.

⑺ About manufacturers, which is more reliable

It is clear that everything that is written below is conditional and not very representative data. Because to make real statistics on the most reliable drives, you need to test thousands of drives (and not several dozen, as I did). However, I'll give my opinion...

1. WD My Passport is one of the most reliable, not a single drive from this line has failed. Yes, and there are no particular complaints about the work: they do not make noise, do not heat up, they are always "visible". The price tag is 10-15% higher on them than on other similar drives, but they are worth it. I will add that their dimensions are also somewhat larger than those of the same Seagate Portable Slim (but in my opinion this is not significant) ...
2. WD My Cloud - in principle, everything that is said above is also relevant for this line;
3. Toshiba Canvio - despite the fact that the discs appeared on the market not so long ago, there are no particular complaints about them. So far there have been no problems with any of the 4 disks;
4. Seagate Expansion - average in quality (5 out of 7 drives work, 2 were delivered under warranty, didn't work even for a year...). There are no problems with "visibility", but I would note that many drives from this line "noise" during operation;
5. Seagate Portable Slim - in my opinion, the worst line (everywhere where "Seagate Slim" is found - it is better to beware!). It is possible that I was just unlucky, but 5 out of 5 disks fell into disrepair within 1.5 years after purchase;
6. A-DATA - in general they work (4 out of 5 drives have been working for more than a year), but drives from this manufacturer do not always have enough USB power when used on laptops;
7. Transcend StoreJet is an interesting option because their discs are protected by special. body from light shocks. There were no questions about reliability (although I only have 2 of them), there is a problem with "noise" during operation and "visibility" without additional. nutrition;
8. Silicon Power (Armor) - negative review, because 3 out of 3 disks didn't live up to even the initial expectations: the data transfer rate is low (even when connected to USB 3.0), often "fall off" and become invisible. Not work - but a nightmare ...

And what do you use?

SSDVerbatimStore " n" Go: for work and play!

External testing SSDdriveVerbatimStore " n" GoUSB 3.1 GEN1 with a capacity of 240 gigabytes (53231).

Introduction

The recent trend towards replacing classic hard drives SSD storage continues to gain momentum. They have already taken root not only in PCs and laptops, but also in cases of portable storage devices.

Verbatim Keypad Secury USB 3.0 flash drive test.

Verbatim Keypad Security -yourpocketsafe!

Flash drive testing VerbatimKeypadSecurityUSB 3.0

Introduction

Continuing the topic of secure data storage, we would like to introduce you to a very interesting and original product -VerbatimKeypadSecurityUSB 3.0.

Verbatim Fingerprint Secure portable hard drive test with built-in fingerprint scanner.

Verbatim Fingerprint Secure:tothisfingerapply!

portable testing hard drive VerbatimFingerprintsecurewith USB 3.0 interface, dual protection technology, 1TB capacity.

Introduction

Imagine a very real situation - you need to transfer large files to colleagues or friends, but you cannot do it yourself. But you can ask your friends to bring them a portable hard drive with the necessary information. But you don't want the information written on it to fall into the wrong hands. How to be in this case?

Verbatim ToughMAX and Pin Stripe 64 GB USB flash drive test.

Affordable and secure!

Testing 64 GB USB Drives VerbatimToughMAX and Pin Stripe.

Introduction

USB flash drives have long and firmly entered our lives and the demand for them is constantly growing. It is already difficult to imagine how we used to do without these compact, capacious and convenient storage media.

Verbatim Vx500 external SSD test with USB 3.1 Gen 2 interface.

VerbatimVx500 - "space speeds" of data exchange!

External testing SSDdriveVerbatimVx500 USB 3.1 Gen 2 240 GB (model 47442).

Introduction

The topic of portable storage drives is always of great interest. Moreover, the requirements for these devices are constantly growing not only in terms of data volume, but also in terms of write / read speed.

Verbatim Store "n" Go Lightning USB 3.0 Flash Drive Test.

One in two!

Combo Flash Drive Testing VerbatimStore " n" GoLightningUSB 3.0 with Lightning and USB 3.0 interfaces.

Introduction

Reviewing the company's product range verbatim, we drew attention to a very interesting flash drive from the familyStore " n" Go. The fact is that, thanks to the presence of ports Lightning and USB 3.0 can work with most popular computers, smartphones and tablets.

We have taken this product to the test with great interest. And our review of the workVerbatimStore " n" GoLightningUSB 3.0 read below.

Test microSDXC memory card for portable devices Verbatim Pro U3 16GB.

Durability, reliability and quality!

microSD testing XCflash cards Verbatim Pro U3 16GB to work with 4 Kvideo.

Introduction

We have already written more than once that modern gadgets occupy a very important place in our life, and we most often store most of the necessary information on them. Therefore, the choice of media that we use in them should be approached responsibly. After all, it is to them that we entrust important personal information, which will be very disappointing to lose.

Considering this, our next test of data storage devices we decided to dedicate microSD XCmemory card designed for portable devices Verbatim Pro U3.

The manufacturer positions the flash drive as a device for storing media data up to format 4 K.

Well, read about the work of the carrier below.

Store "n" Go 500 GB USB 3.0 portable hard drive test (model 53196).

Gigabytes to go!

Store "n" Go USB 3.0 500 GB Portable Hard Drive Test (Model 53196).

Introduction

The topic of portable hard drives, judging by the letters of our readers, is very popular and in demand. Therefore, we decided to continue our acquaintance with a series of discs Store "n" Go fromVerbatim. After all, the drives of this series are positioned by the company as high-speed and very reliable devices at an affordable price.

Our series of publications continues with a story about work hard disk Store "n" Go (Model 53196) with port USB 3.0 with a capacity of 500 gigabytes.

Verbatim Pro U3 32GB SDHC Card test.

Universal "soldier" of the media front!

Verbatim Pro U3 32GB SDHC Card testing.

Introduction

We have repeatedly tested various flash drives with USB port, and now our "tenacious paws" got to the memory cards. We decided to test how their characteristics correspond to the declared ones.

And started with Verbatim Pro U3 32GB SDHC Card. We chose this model based on its high speed characteristics, orientation to work with 4 K video and of course for a very reasonable price.

Introduction

We continue a series of articles about testing products purchased from Uncle Alik (Aliexpress).

In this review, we will share the test results with you SSD drive Londisk familiesAuroravolume 960 GB.

The fact is that we needed to upgrade one of the laptops, but the memory and processor in it were already set to the maximum, and the performance was not enough. And we decided to replace the standard "hard" speed SSD.

As always, having examined the prices of Moscow stores, we decided to save a little, the price was very high for SSD the amount we need. And again our path lay to Uncle Alik. On the site, we chose for a long time from a rich assortment SSD the most suitable option and settled on Londisk Aurora960 GB.

Well, read the results of our “running in” of the device below.

Testing compact external Blu-ray recorder Verbatim with USB 3.0 interface.

Introduction

If you look at the packaging of modern laptops, you can see one very interesting trend. Namely, more and more manufacturers are trying not to install optical drives. And this applies not only to light and compact ultrabooks, even ordinary laptops are increasingly being sold without them.

But sometimes the user needs to create an archive copy of his data for long-term storage and preferably with a guarantee against damage. Previously, in this case, we used CD or DVD carriers. But their capacities by modern standards are very small. Of course, you can use a flash drive or external hard drive but they sometimes fail.

The easiest way out of this situation is to buy an external recorder. Well, given the growth in the volume of user data, the external Blu-ray drive is perfect for this.

Who is interested to know our opinion about the work Verbatim Blu-ray Recorder with USB 3.0 Interface read the review below.

Any electronic computers include memory drives. Without them, the operator would not be able to save the result of his work or copy it to another medium.

Punch cards

At the dawn of its appearance, punched cards were used - ordinary cardboard cards with printed digital markings.

One punched card contained 80 columns, each column could store 1 bit of information. The holes in these columns corresponded to the unit. The data was read sequentially. It was impossible to re-record anything on a punch card, so a huge number of them were required. It would take 22 tons of paper to store a 1 GB data array.

A similar principle was used in perforated tapes. They wound on a reel, took up less space, but often torn and did not allow you to add and edit data.

floppy disks

The advent of floppy disks was a real breakthrough in information technology. Compact, capacious, they allowed to store from 300 KB on the earliest samples to 1.44 MB on latest versions. Reading and writing were carried out on a magnetic disk enclosed in a plastic case.

The main disadvantage of diskettes was the fragility of the information stored on them. They were vulnerable to action and could be demagnetized even in public transport - a trolleybus or tram, so for long-term storage They tried not to use their data. Floppy disks were read in disk drives. At first there were 5-inch floppy disks, then they were replaced by more convenient 3-inch ones.

Flash drives have become the main competitor of floppy disks. Their only drawback was the price, but as microelectronics developed, the cost of flash drives dropped dramatically and floppy disks became history. Their production was finally discontinued in 2011.

streamers

Streamers were previously used to store archived data. They were similar to video cassettes in appearance and in principle. A magnetic tape and two reels made it possible to sequentially read and write information. The capacity of these devices was up to 100 MB. Such drives have not received mass distribution. Ordinary users preferred to store their data on hard drives, and it was more convenient to keep music, films, programs on CDs, and later on DVDs.

CD and DVD

These storage media are still in use today. An active, reflective and protective layer is applied to the plastic substrate. Information from the disc is read by a laser beam. A standard disk has a capacity of 700 MB. This is enough for example to record a 2-hour movie in average quality. There are also double-sided discs where the active layer is deposited on both sides of the disc. Mini-CDs are used to save a small amount of information. Drivers, instructions for computer products are now written on them.

DVDs replaced CDs in 1996. They allowed to store information already in the amount of 4.7 GB. Their advantage was also that the DVD drive could read both CDs and DVDs. On this moment it is the most massive memory storage.

Flash drives

The CD and DVD drives discussed above have a number of advantages - cheapness, reliability, the ability to store large amounts of information, but they are designed for one-time recording. You cannot make changes, add or remove unnecessary things on a recorded disc. And here a fundamentally different drive comes to our aid - flash memory.

For some time he competed with floppy disks, but quickly won this race. The main limiting factor was the price, but now it has been reduced to an acceptable level. Modern computers are no longer equipped with disk drives, so the flash drive has become an indispensable companion for everyone dealing with computer technology. The maximum amount of information that can fit on a flash drive reaches 1 Tb.

Memory cards

Phones, cameras, e-books, photo frames and much more require memory drives to work. Due to their relatively large size, USB sticks are not suitable for this purpose. Memory cards are specially designed for such cases. In fact, this is the same flash drive, but adapted for small-sized products. Most of the time, the memory card is in an electronic device and is removed only to transfer the accumulated data to a permanent medium.

There are many standards for memory cards, the smallest of them are 14 by 12 mm. On modern computers instead of a disk drive, a card reader is usually placed, which allows you to read most types of memory cards.

Hard drives (HDD)

Memory drives for a computer are inside it there are metal plates coated on both sides with a magnetic composition. The motor rotates them at a speed of 5400 for older models or 7200 rpm for modern devices. The magnetic head moves from the center of the disk to its edge and allows you to read and write information. The volume of the hard drive depends on the number of disks in it. Modern models allow you to store up to 8 Tb of information.

There are practically no shortcomings of this type of memory drives - they are very reliable and durable products. The cost of a unit of memory in hard drives is the cheapest among all types of drives.

Solid state drives (SSD)

No matter how good hard drives are, they have almost reached their ceiling. Their performance depends on the speed of disk rotation, and its further increase leads to physical deformation. Flash technology, which is used in the manufacture of solid-state memory drives, is devoid of these disadvantages. They do not contain moving parts, so they are not subject to physical wear and tear, are not afraid of shock and do not make noise.

But there are still serious shortcomings. First of all - the price. Price solid state drive 5 times higher than a hard disk of the same size. Another significant drawback is a short service life. Solid State Drives usually choose to install operating system and the hard disk is used for data storage. Price solid state drives is steadily declining, there is progress in increasing their resource. In the near future, they should replace traditional hard drives, just as flash drives replaced floppy disks in their time.

External drives

internal storage and inner memory are good for everyone, but it is often necessary to transfer information from one computer to another. Back in 1995, the USB interface was developed, which allows you to connect a wide variety of devices to a PC, and memory drives are no exception. At first, these were flash drives, later DVD players with a USB connector appeared, and, finally, HDD drives and SSD.

The attractiveness of the USB interface is in its simplicity - just plug in a USB flash drive or other storage device and you can work, no driver installation or other additional steps are required. The development of the interface and the appearance of USB 2.0 first, and then USB 3.0, dramatically increased the speed of data exchange over this channel. The performance now differs little from the internal one, and their size cannot but rejoice. An external memory drive fits easily in the palm of your hand, while it allows you to store hundreds of gigabytes of information.

03.03.2018

Data storage. Internal and external memory drives. Types of memory drives

A storage device is a device on which all computer data is stored. In addition to the drive, this device is called a hard drive or hard drive. A hard disk differs from a conventional “floppy” disk, or in other words, a floppy disk, in that information is recorded on hard plates made of aluminum or ceramics, and on top they are covered with a ferrimagnetic material. Hard drives are equipped with one or more platters on an axle.

The data storage device (HDD) is composed of a sealed unit and an electronic board. The hermetically sealed unit is filled with normal, dust-free air by atmospheric pressure and is equipped with all mechanical parts. The kinematics of the data drive includes one or more magnetic disks, which are rigidly fixed to the motor spindle, as well as a system responsible for positioning the magnetic heads. The magnetic head occupies a place on one of the sides of the moving magnetic disk and its functional duties include reading and writing data from the rotating surface of the magnetic disk. The heads themselves are attached with special holders, and their movement is carried out using a positioning system between the edge and the center of the disk. It is possible to achieve precise positioning of magnetic heads by means of servo information recorded on the disk. The positioning system, reading this information, is able to determine the strength of the current passed through the coil of electromagnetic wire so that the magnetic head can be fixed over the required track.

After the power is turned on, the processor of the hard drive (drive) begins to test the electronics, after which a command is issued to enable the process of directly turning on the spindle motor. As soon as the initialization is completed, the positional system is tested, during which the tracks are enumerated in the specified sequence. If the test went well, the hard drive sends a signal that it is ready to go. To increase the level of reliability of computer information storage, hard drives (drives) are equipped with a special firmware that monitors the technological parameters available for the reading and analysis program. If the computer is in danger of failure, then with the help of this program the user will know about it in a timely manner.

In addition, the data storage is hybrid hard a disk that consists of a traditional hard drive equipped with additional flash memory. This flash memory is completely non-volatile and is assigned the role of a buffer in which the most frequently used data is stored. As a result of the activity of this device, access to the magnetic disk is reduced, which accordingly leads to a decrease in power consumption. Also, the level of reliability of storing information is increased, the time required to boot and to wake the system from sleep mode is reduced, and the temperature and acoustic noise that the hard drive emits are significantly reduced.

The attractiveness of the USB interface is in its simplicity - just plug in a USB flash drive or other storage device and you can work, no driver installation or other additional steps are required. The development of the interface and the appearance of USB 2.0 first, and then USB 3.0, dramatically increased the speed of data exchange over this channel. The performance now differs little from the internal one, and their size cannot but rejoice. An external memory drive fits easily in the palm of your hand, while it allows you to store hundreds of gigabytes of information.

Introduction

1. Magnetic drives

1.1 Magnetic disk drives

2. Types of magnetic media

2.1 Floppy disks

3. Optical technology

3.1 CDs

3.2 DVD media

Conclusion

Bibliography

magnetic media hard magnetic

Introduction

The information storage devices produced are a range of storage devices with different operating principles, physical and technical performance characteristics. The main property and purpose of information storage devices is its storage and reproduction.

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 digital information reproduction/recording storage technology. Therefore, in connection with the type and technical design of the information carrier, there are: electronic, disk and tape devices.

Magnetic disks are used as storage devices that allow you to store information for a long time, when the power is off. To work with magnetic disks, a device called a magnetic disk drive (MDD) is used. The main types of drives: floppy disk drives (FPHD); hard disk drives (HDD); magnetic tape drives (NML); CD-ROM drives, CD-RW, DVD.

They correspond to the main types of media: floppy disks (Floppy Disk); hard magnetic disks (Hard Disk); cassettes for streamers and other NML; CD-ROMs, CD-Rs, CD-RWs, DVDs.

1. Magnetic drives

Magnetic drives are the most important medium for storing information in a computer and are divided into magnetic tape drives (NML) and magnetic disk drives (NMD).

Typically, magnetic recording uses pulsed signals. Bit information is converted into alternating current in accordance with the alternation of zeros and ones.

This current enters the magnetic head and, depending on the direction of the current in the head winding, a corresponding magnetic flux arises in the space between the head and the carrier, which closes through an elementary region of magnetization (domain). The intrinsic magnetic fields of the domains are oriented in accordance with the direction of the external magnetic field. When the external field is removed, this state of the domains does not change (long-term storage).

The main criterion for evaluating magnetic storage media is the surface recording density. It is defined as the product of the linear recording density along a track, expressed in bits per inch, and the number of tracks per inch. As a result, areal recording density is expressed in megabits (Mbps) or gigabits (Gbps) per square inch.

In modern 3.5-inch drives, this parameter is 10-20 Gb / inch, and in experimental models it reaches 40 Gb / inch. This allows the production of drives with a capacity of more than 400 GB.

1.1 Magnetic disk drives (MDDs)

NMD provides a similar NML possibility of sequential access to information. A magnetic disk drive combines several sequential access devices, and the reduction in data search time is ensured due to the independence of access to a record from its location relative to other records.

NMD technology. In NMD, as data carriers, a package of metal disks (or platters) is used, fixed on a rod, around which they rotate at a constant speed. The surface of a magnetic disk covered with a ferromagnetic layer is called the working surface.

The number of magnetic heads is equal to the number of working surfaces on one disk pack. If the package consists of 11 disks, then the access mechanism consists of 10 holders with two magnetic heads on each of them. The magnetic head holders are combined into a single block in such a way as to ensure their synchronous movement along all cylinders. The set of tracks achieved with a fixed position of the head unit is called a cylinder. The distance between the cylinders (tracks) is called the pitch, or track pitch. The process of controlling the recording density is called pre-compensation. To compensate for different recording densities, the zone-sector recording method (ZoneBitRecording) is used, where the entire disk space is divided into zones (eight or more), each of which usually includes from 20 to 30 cylinders with the same number of sectors.

In the zone located on the outer radius (the junior zone), more sectors (blocks) are recorded per track (120-96). Towards the center of the disk, the number of sectors decreases and in the oldest zone reaches 64-56. Since the speed of rotation of the disk is a constant value, more information is received from the outer zones during one revolution of the disk than from the inner zones. This non-uniformity of information receipt is compensated by an increase in the speed of the data reading / conversion channel and the use of special tunable filters for frequency correction by zones. The capacity of hard drives can be increased by approximately 30%.

1.2 Hard disk drives

The design and operation of the device. The HDD has several platters (discs) or platters installed inside the drive. The plates are either 5.25" or 3.5" in diameter. New designs are trying to use glass because it has more resistance and will allow thinner discs than aluminum counterparts.

Characteristics of HDD. The characteristics of a hard drive are very important in evaluating the performance of the system as a whole. The effective performance of a hard drive depends on a number of factors.

Decisive among them is the speed of disk rotation, which is measured in rpm (rpm) and directly affects the data transfer speed in the hard drive. While the fastest EIDE hard drives were around 5400 rpm, SCSI HDDs can go up to 7200 rpm. The median drive access time is the interval between the time data is requested and the time data is accessed (measured in milliseconds (ms)). Access time includes actual search time, wait time, and data processing time.

Seek Time - The total time required for the read/write head to find the physical location of the data on the disk. The latency is the average access time to a sector during a rotation. It is easily calculated from the speed of rotation of the drive axis as a half-turn time.

A disk's transfer rate (sometimes called media speed) is the speed at which data is transferred to and read from a disk drive. It depends on the recording frequency and is usually measured in megabytes per second (MBps, MB/s).

The data transfer rate (or DTR- DataTransferRate) is the rate at which a computer can transfer data over buses (usually IDE/EIDE or SCSI) to the CPU. Some data providers specify an internal transfer rate, transferring data from the head to the built-in disk buffer. Others cite the data burst rate, the maximum data rate for ideal parameters, or for short duration. The speed of external data transfer is more important.

2. Types of magnetic media

2.1 Floppy disks

A floppy disk consists of a round polymer substrate coated on both sides with magnetic oxide and placed in a plastic package, the inner surface of which is coated with a cleaning coating. The package has radial slots on both sides through which the drive's read/write heads gain access to the disk.

Floppy disks of each size are usually double-sided. Single track density is 48 tpi (tracks per inch), double density is 96 tpi, and high density is typically 135 tpi.

When a 3.5" drive is inserted into the device, the protective metal shutter is pulled back, the drive spindle enters the middle hole, and the drive's side pin is placed in a rectangular positioning hole nearby. The motor spins the drive at 300 rpm.

Floppy disk drives use what's called "open loop tracking", they don't actually look for tracks, they just set the head to the "correct" position. In hard disks, by contrast, servo motors use heads to check positioning, which allows recording at a cross-sectional density many hundreds of times higher than is possible on a floppy disk.

The head is moved by the lead screw, which is in turn controlled by a stepper motor, and when the screw turns a certain angle, the head travels the set distance. The density of data recording on a floppy disk is limited by the accuracy of the stepper motor, in particular, this means 135 tpi for 1.44 MB floppy disks. The disk has four sensors: disk motor; write protection; the presence of a disk; and track sensor 00.

2.2 External hard drives

In recent years, technologies have spread to place standard hard drives in a mobile (portable) external case (box), which is connected to a computer via an external interface.

Since today the capacity of a hard drive is measured in gigabytes, and the sizes of multimedia and graphic files are measured in tens of megabytes, a capacity of 100 to 150 MB is enough for the media to fill the traditional niche of a hard drive - moving several files between users, archiving or backing up individual files or directories, and forwarding files by mail. This range offers a range of next-generation floppy drives that use floppy media and traditional magnetic storage technology.

Zi p-accumulators. Without a doubt, the most popular device in this category is the ZipIomega drive, first released in 1995. The high performance of Zip drives is ensured, firstly, high speed rotation (3000 rpm), and secondly, the technology proposed by Iomega (which is based on the aerodynamic Bernoulli effect), while the floppy disk "sticks" to the read / write head, and not vice versa, as in the HDD. Zip drives are soft like floppy drives, making them cheaper and less susceptible to shock loads.

Zip drives have a capacity of 94 MB and are available in both built-in and external versions. Internal modules conform to 3.5" form factor, use SCSI or ATAI interface, average seek time - 29 ms, data transfer rate - 1.4 Kbps.

Superdiskettes. The range from 200 to 300 MB best corresponds to the concept of superfloppy territory. The capacity of such devices is 2 times higher than that of the floppy disk substitute, and is more typical for an HDD than for a floppy disk. Devices in this group use magnetic or magneto-optical technology.

In 2001, Matsushita announces the FD32MB technology, which gives the option of high-density formatting a conventional 1.44 MB HB floppy disk to provide storage capacity of up to 32 MB per disk. The technology consists in increasing the recording density of each track on an HD floppy using a superdisk magnetic head for reading and a conventional magnetic head for writing data. While a conventional floppy disk has 80 circular data tracks, the FD32MB increases this number to 777. At the same time, the track feed from 187.5 µm for an HD diskette is reduced to about 18.8 µm.

Replaceable hard drives. The next capacity interval (from 500 MB to 1 GB) is enough to back up or archive a disk partition (partition) of a reasonably large size.

In the range above 1 GB, the removable disk technology is borrowed from conventional HDDs. Released in mid-1996, the IomegaJaz disk drive (replaceable 1 GB hard drive) was hailed as an innovative product. When Jaz hit the market, it was immediately clear where to use it - users were able to create audio and video presentations and transfer between computers. In addition, such presentations could be run directly from the Jaz media, without the need to rewrite the data to the hard drive.

Flash memory. Not related to magnetic media, flash memory works simultaneously like RAM and hard drive. It resembles ordinary memory, having the form of discrete chips, modules, or memory cards, where, just like in DRAM and SRAM, data bits are stored in memory cells. However, just like HDD, flash memory is non-volatile and retains data even when the power is turned off.

ETOX technology is the dominant flash technology, accounting for about 70% of the entire non-volatile memory market. Data is entered into the flash memory bit by bit, byte by byte, or words by an operation called programming.

While electronic flash drives are small, fast, consume little power, and can withstand shocks of up to 2000g without destroying data, their limited storage capacity makes them an inappropriate alternative to a PC hard drive.

3. Optical technology

3.1 CDs

In the beginning, CDs were used exclusively in high-quality sound-reproducing equipment, replacing obsolete vinyl records and tape cassettes. However, laser discs soon began to be used on personal computers. Computer laser discs were called CD-ROM. In the late 90s. a CD-ROM device became a standard component of any personal computer, and the vast majority of programs began to be distributed on CDs.

Compact disc drive (CD-ROM). Information is read from a CD using a laser beam of lower power. The servomotor, on command from the drive's internal microprocessor, moves the reflecting mirror or prism. This allows the laser beam to be focused on a particular track. The laser emits coherent light, consisting of synchronized waves of the same length. The beam, hitting a light-reflecting surface (platform), is deflected through a splitting prism to a photodetector, which interprets this as "1", and falling into a recess (pit), it is scattered and absorbed - the photodetector fixes "0".

While magnetic disks rotate at a constant RPM, i.e. at a constant angular speed, a CD usually rotates at a variable angular speed to ensure a constant linear speed when reading. Thus, the reading of internal tracks is carried out with an increased, and external - with a reduced number of revolutions. This is what causes more low speed data access for CDs compared to hard drives.

3.2 Media DVD

A universal digital disc (digitalversatiledisc- DVD) is a type of storage device that, unlike a CD, has been designed for widespread use in both the audio-video and computer industries since it entered the market. DVDs are the same size as a standard CD (diameter 120 mm, thickness 1.2 mm), provide up to 17 GB of memory at a transfer rate higher than CD-ROM, have access times similar to CD-ROM, and are divided into four versions:

DVD-5 - single-sided single-layer disc, with a capacity of 4.7 GB;

DVD-9 - 8.5 GB single-sided double-layer disc;

DVD-10 - double-sided single-layer disc 9.4 GB;

DVD-18 - capacity up to 17 GB on a double-sided double-layer disc.

DVD - ROM. As with the discs themselves, there are few differences between DVD and CD-ROM drives, as the only obvious thing is the DVD logo on the front. The main difference is that the CD-ROM data is written close to the top layer of the disc's surface, while the DVD data layer is closer to the middle so that the disc can be double-sided. Therefore, the optical reading unit of a DVD-ROM drive is more sophisticated than its CD-ROM counterpart to allow for reading either one or the other of these media types.

One of the earliest solutions was to use a pair of swiveling lenses, one to focus the beam on DVD data levels and the other to read normal CDs. Subsequently, more sophisticated designs have emerged that eliminate the need to switch lenses. For example, Sony's "double discrete optical sampling" has separate lasers optimized for CD (780nm) and DVD (650nm). Panasonic devices switch laser beams using a holographic optical element capable of focusing the beam at two different discrete points.

DVD-ROM drives spin a disc much more slowly than their CD-ROM counterparts. However, since the data is packed much denser on a DVD, its performance is significantly higher than that of a CD-ROM at the same rotation speed. While a normal audio CD-ROM (lx or single) has a maximum data transfer rate of 150Kb/s, a DVD(1x) can transfer data at 1250Kb/s, which is only achieved at eight times (8x) the speed of a CD-ROM .

There is no generally accepted terminology to describe the various "generations" of DVD drives. However, the term "second generation" (or DVDII) usually refers to 2x speed drives that are also capable of reading CD-R/CD-RW media, while the term "third generation" (or DVDIII) usually refers to 5x (or sometimes 4x) speed drives. ,8x, or 6x), some of which are capable of reading DVD-RAM media.

Recordable disc formats DVD

There are several versions of recordable DVDs:

DVD-R regular, or DVD-R;

DVD-RAM(rewritable);

recordable DVD . DVD-R (or recordable DVD) is conceptually similar to CD-R in many ways - it is a write-once media that can contain any type of information normally stored on a mass-produced DVD - video, audio, pictures, data files, programs, multimedia, etc. e. Depending on the type of information being recorded, DVD-R discs can be used on virtually any compatible DVD playback device, including DVD-ROM drives and DVD video players. Since the DVD format supports double-sided discs, up to 9.4 GB can be stored on a double-sided disc. DVD-R disc. Data can be written to DVD at 1x speed (11.08 Mbps, which is approximately equivalent to 9x CD-ROM speed). Once burned, DVD-R discs can be read at the same speeds as mass-produced discs, depending on the x-factor (multiple of the speed) of the DVD-ROM drive being used.

DVD-R, like CD-R, uses constant line rate (CLV) to maximize recording density on the disc surface. This requires a change in revolutions per minute (rpm) as the track diameter changes as one moves from one edge of the disc to the other. The recording starts on the inside and ends on the outside. At 1x speed, the rotation speed varies from 1623 to 632 rpm for a 3.95 GB disc and from 1475 to 575 rpm for a 4.7 GB disc, depending on the position of the record-playback head on the surface. For a 3.95 GB disc, the track spacing (pitch), or the distance from the center of one turn of a spiral track to the adjacent portion of a track, is 0.8 microns (microns), half that of CD-R. On a 4.7 GB disk, an even smaller track feed is used - 0.74 microns.

DVD - RAM . The rewritable DVD-ROM or DVD-RAM uses phase change technology, which is not a purely optical technology of CD and DVD, but a combination of some features of magneto-optical methods and has its origins in optical disc systems. The applied format "surface-groove" (landgroove) allows you to record signals both on the recesses formed on the disk, and in the gaps between the recesses. Recesses and sector headers are formed on the surface of the disc during its casting.

In mid-1998, the first generation of reusable DVD-RAM products appeared with a capacity of 2.6 GB on both sides of the disc. However, these early devices are not compatible with higher capacity standards that use a contrast enhancement layer and a thermal buffer layer to achieve higher recording densities. The specification for DVD-RAM version 2.0 with a capacity of 4.7 GB on one side was released in October 1999.

DVD - RW . Formerly known as DVD-R/W or DVD-ER, DVD-RW media (which became available in late 1999) is part of Pioneer's evolutionary development of existing CD-RW/DVD-R technologies.

DVDs-RW use the technology of changing the phase state of matter for reading, writing and erasing information. A 650 nm laser beam heats the sensitive alloy layer to either crystalline (reflective) or amorphous (dark, non-reflective) depending on the temperature level and subsequent cooling rate. The resulting difference between the recorded dark marks and the erased reflective marks is recognized by the player or drive and allows the stored information to be reproduced.

DVD-RW media uses the same physical addressing scheme as DVD-R media. During the recording process, the drive's laser follows the microscopic depression, writing data in a spiral track.

One of the main advantages of the third DVD-DVD+RW rewritable format is that it provides better compatibility than any of its competitors.

DVD + RW . The DVD-RAM specification was a compromise between two different offerings from major competitors - the Hitachi grouping, Matsushita Electric and Toshiba, on the one hand, and the Sony/Philips alliance on the other.

DVD+RW shares many similarities with competing DVD-RW technology in that it uses phase change media and assumes the user experience obtained with CD-RW discs. DVD+RW discs can be recorded in either constant linear velocity (CLV) for sequential video recording or constant angular velocity (CAV) for direct access.

DVD + R . The two-layer DVD+R system uses two thin organic films of the material to be dyed, separated by a spacer (filler). Heating by a concentrated laser beam irreversibly changes the physical and chemical structure each layer so that the modified areas receive optical properties different from the original ones. This causes the reflectivity to fluctuate as the disc rotates and creates a read signal similar to that found in stamped DVD-ROM discs.

Conclusion

Thus, the following general conclusions can be drawn:

1. Magnetic drives are the most important medium for storing information in a computer and are divided into magnetic tape drives (NML) and magnetic disk drives (NMD).

2. Magnetic disks are used as storage devices that allow you to store information for a long time, when the power is off.

3. The main types of drives: floppy disk drives (FPHD); hard disk drives (HDD); magnetic tape drives (NML); drives CD-ROM, CD-RW, DVD.

4. The main types of media: flexible magnetic disks (Floppy Disk); hard magnetic disks (Hard Disk); cassettes for streamers and other NML; CD-ROMs, CD-Rs, CD-RWs, DVDs.

5. There are several versions of recordable DVDs: DVD-R regular or DVD-R; DVD-RAM(rewritable); DVD-RW; DVD+RW.

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