How to store information for a long time. Classification of long-term storage devices for long-term storage of user information serves

Classification of devices of long-term storage of information

The most common are the storage devices on magnetic disks, which are divided into rigid magnetic disks (HDD) and drives on flexible magnetic disks (NGMD), and drives on optical disks, such as CD-ROM drives, CD-R, CD-RW and DVD-ROM.

Detailed characteristics of long-term storage devices

· Storage drives on hard magnetic disks (NGMD)

The NJMD is the main device for long-term storage of large amounts of data and programs. Other names: Hard disk, Winchester, HDD (Hard Disk Drive). Externally, the Winchester is a flat, hermetically closed box, inside of which are located on the total axis of a few rigid aluminum or glass circular plates. The surface of any of the disks is covered with a thin ferromagnetic layer (a substance that responds to an external magnetic field) is actually stored on it recorded data. At the same time, the recording is carried out on both surfaces of each plate (except extreme) with a block of special magnetic heads. Each head is above the working surface of the disk at a distance of 0.5-0.13 μm. The disk package rotates continuously and with a high frequency (4500-10000 rpm), so the mechanical contact of the heads and disks is unacceptable.

There are a huge number of different models of hard drives of many firms, such as Seagate, Maxtor, Quantum, etc. To ensure the compatibility of hard drives, the standards for their characteristics that determine the nomenclature of the connecting conductors are developed, their placement in transition connectors, electrical parameters of signals. Integrated Drive Electronics or ATA and SCSI and SCSI (Small Computer System Interface) are common are common. "INTEGRATED DRIVE ELECTRONICS) / INTEGRATED DRIVE ELECTRONICS The characteristics of the interfaces by which the hard drives are associated with the motherboard, largely determine the performance of modern hard drives.

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

  • § Disc circulation speed - EIDE drives are produced in our time with a circulation frequency of 4500-7200 rpm, and SCSI drives - 7500-10000 rpm;
  • § Cache-memory capacity - In all modern disk drives, a cache buffer is installed, accelerating data exchange; The more its capacity, the higher the likelihood that in the cache memory will be the necessary information that does not need to be read from the disk (this process is thousands of times slower); Cache buffer capacitance in different devices may vary within borders from 64 KB to 2 MB;
  • § Average access time - time (in milliseconds), during which the head block shifts from one cylinder to another. Depends on the design of the drive of the heads and is approximately 10-13 milliseconds;
  • § Delay time - this time from the time of positioning the head block to the desired cylinder before positioning a specific head to a specific sector, in other words, this is the time of searching for the desired sector;
  • § exchange rate - determines the amount of data that can be transmitted from the drive to the microprocessor and in the opposite direction for certain intervals; 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 when the central processor is directly involved, the greater the PIO number number, the higher the exchange rate; DMA (Direct Memory Access) allows you to transfer data directly to RAM without processor; The data transfer rate in modern hard drives ranges in the range of 30-60 MB / s.
  • · Drives on flexible magnetic disks (NGMD)

NGMD or drive is mounted in the system unit. Flexible NGMD media are produced in the form of a diskette (another name of the floppy disk). Actually, the carrier is a flat disk with a special, sufficiently dense film covered with a ferromagnetic layer and placed in a protective envelope with a movable valve at the top. The floppy disks are mainly used for the operational transfer of small amounts of information from one computer to another. Data recorded on a diskette can be protected from erasing or overwriting. To do this, you need to move the small protective valve at the bottom of the floppy disk, so that the open window is formed. In order to allow recording, this valve should be moved back and close the window.

The main parameters of the diskette is the technological size (in inches), the record density and complete capacity. In size, there are 3.5-inch floppy disks and 5,25-inch diskettes (no longer used). Record density can be a simple SD (SINGLE DENSITY), dual DD (Double Density) and High HD (High Density). The standard capacity of the 3.5-inch floppy disk is 1.44 MB, it is possible to use a diskette with a capacity of 720 KB. Currently, the standard is a 3.5-inch floppy disks, high HD density having a capacity of 1.44 MB.

· CD-ROM drive

Since 1995, in the basic configuration of a personal computer, instead of 5.25 inches drives, a CD-ROM drive has begun. CD-ROM Abbreviation (Compact Disk Read Only Memory) is translated as a constant storage device based on CDs. The principle of operation of this device consists in reading digital data using a laser beam, which is reflected from the surface of the disk. A regular CD CD is used as a media. The digital record on the CD differs from high density on magnetic discs, so the standard CD has a capacity of about 650-700 MB. Such large volumes are characteristic of multimedia information (graphics, music, video), therefore CD-ROM drives refer to multimedia hardware. In addition to multimedia publications (e-books, encyclopedias, music albums, videos, computer games) CDs are distributed a variety of systemic and application software for large volumes (operating systems, office packages, programming systems, etc.).

CDs are made of transparent plastic with a diameter of 120 mm and a thickness of 1.2 mm. A layer of aluminum or gold is sprayed on the plastic surface. Under mass production, record information on the disk occurs by extrusion on the surface of the track, in the form of a number of recesses. This approach provides binary recording of information. Deepete (Pit - Pete), Surface (Land - Land). Logical zero can be represented as peit and land. The logical unit is encoded by the transition between peet and land. From the center to the edge of the CD, the only path in the form of a spiral of a 4 micron width with 1.4 micron increments. The surface of the disk is divided into three areas. 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 records, the disc label and other service information. The average area contains basic information and takes most of the disk. The final area (LEAD-OUT) contains a label of the end of the disk.

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

The main characteristics of CD-ROM:

  • § Data transfer rate - is measured in multiple volumes of the speed of the audio CD player (150 KB / s) and characterizes the maximum speed with which the drive forwards data into the computer's RAM, for example, 2-speed CD-ROM (2x CD-ROM) will be Receive data at a speed of 300 KB / s., 50-speed (50x) - 7500 KB / s.;
  • § Access time - the time required to search for information on the disk is measured in milliseconds.

The main disadvantage of standard CD-ROM is the impossibility of data recording, but there are CD-R and multi-sized CD-RW records.

· CD-R drive (CD-RECORDABLE)

Externally similar to CD-ROM drives and compatible with them on disk size and recording formats. Allow one disposable entry and unlimited readings are allowed. Data recording is carried out using special software. The recording speed of modern CD-R drives is 4x-8x.

· CD-RW drive (CD-Rewritable)

Used to multiple data recording, and you can just add new information to free space, and completely overwrite the disk with new information (previous data is destroyed). As in the case of CD-R drives, it is necessary to install special programs in the system, and the recording format is compatible with the usual CD-ROM. The recording speed of modern CD-RW drives is 2x-4x.

· DVD drive (DIGITAL VIDEO DISK)

A device for reading digital video recordings. Externally, the DVD is similar to the usual CD-ROM (diameter - 120 mm, a thickness of 1.2 mm), but differs from it by the fact that on one side of the DVD, up to 4.7 GB can be recorded, and on two - to 9.4 GB. In the case of the use of a two-layer recording scheme on one side, you can accommodate up to 8.5 GB of information, respectively, on two sides - about 17 GB. DVDs allow rewriting information.

· DVD perspectives

The presence of different standards and specifications does not mean that DVD technology is in place. The efforts of various companies today are aimed at introducing the technology of a "blue laser" with a smaller wavelength. This will increase the recording density on the disks with the improvement and other characteristics arising from here.

Calimetrics Inc invited ML technology (Multilevel), which allows three times to increase the capacity of standard DVD / CD. At the same time, there is no need to perform any refinement in the mechanism and optics of existing drives. To implement a new technology, it is enough to use a set of chips developed by this company. The essence of the technology is to be able to use as an information characteristic, the depth of peits (up to 8 levels) when working with disks. Note that similar technology, but for CD discs, is developing a TDK company in collaboration with other firms.

  • · DVD formats read only
  • W DVD-ROM (Digital Versatile Disc Read Only Memory)

DVD-ROM disks are designed for use in computer technology. Information is entered on the disk only time - in its production.

The progress of DVD devices largely repeats the path passed by CD, and is directed mainly on improving the speed characteristics and the introduction of the recording function. The first generation DVD-ROM devices used the CLV mode and read from the disk at a speed of 1.38 MB / s (in the traditional designation for DVDs it is 1x). The second-generation devices could read the DVD from twice the speed - 2x (2.8 MB / s). Modern DVD-ROM - third-generation devices - use the rotation control mode (CAV) with a maximum read speed of 4x-6x (5.5 - 8.3 MB / s) and more. Modern DVD-ROM drives (drives) support reading almost all formats, including CD discs.

DVD-Video format is designed to store and play video. Like a DVD-ROM, this specification determines the ability to read information only - playback of records using video player (video discoders). The specification is based on the DVD-ROM format, but provides for a special way to place data that prevents the disk copying option. Video films in the encoded form are placed on the disk in the process of its production. Playing a DVD-Video is possible only on household video player (video discs) or on DVD drives connected to a computer. When using computer equipment, information decoding is carried out either hardware or software. Modern specification provides an entry to a disc of high-quality video (up to 2 hours in MPEG-2 compression format). As well as multichannel audio support in 8 languages, selection of on-screen format, titers in 32 languages, interactive control via the on-screen menu, up to 9 corner viewing directions, protection against illegal copying, distinction of video product viewing by region, the management of children's access to video materials.

New generation of musical format after CD. The format specification defines high-quality multi-channel sound, support for a wide range of sound quality (quantization 16, 20, 24 bits at a frequency of 44.1 to 192 kHz), playback of DVD players CD discs, support for additional information (including video, text, menu, screensavers, Convenient navigation system), communication with information support Web sites, expanding opportunities when new technologies appear.

There are two versions of DVD-AUDIO format: just a DVD-Audio - only for sound content and DVD-Audiov - for sound with additional information.

Special disk protection measures from pirated copying are developed.

  • · DVD formats for multiple recording
  • W multiple recording

All known specification of rewritable DVD discs use multiple recording technology based on the physical principle of the phase state change (crystalline / amorphous) information layer under the influence of a laser with a wavelength of 650 (635) Nm (Phase-Change Recording). The reading of information is carried out by determining the optical characteristics of the information layer in its various phase states when reflecting the laser rays (the same as when recording).

W DVD-RAM (Digital Versatile Disc Random Access Memory)

Overwritten format developed by Panasonic, Hitachi, Toshiba.

The format is approved by the DVD forum in July 1997. Equipment and disks of this format were tested for 3 months in more than 20 computer manufacturing companies around the world. Over 160 forum participants voted for the adoption of the specification. Today it is the most common DVD format in the computer industry.

DVD-RAM drives read DVD-ROM discs. In turn, DVD-RAM discs can be read only by the DVD-ROM drives of the so-called third generation, manufactured from mid-1999.

The first generation of DVD-RAM discs contained 2.6 GB to the side. Modern - second-generation discs are 4.7 GB on the side or 9.4 GB for bilateral modification.

Two types of one-sided DVD-RAM disks are available - in the cartridge and without a cartridge. Cartridge discs are mainly designed for household video equipment, where it is necessary to eliminate the effect of external factors with intensive manual use. Cartridges in turn can be two species - open and solid.

The most important advantages of DVD-RAM disks are the ability to overwrite up to 100,000 times and the presence of a recording error correction mechanism.

The largest number of overwriting cycles among all DVDs, error correction mechanism and arbitrary disk access, both when recording and when reading, predetermined the maximum efficiency of this format in secondary storage devices. The overwhelming majority of mass storage devices are robotic DVD libraries - uses this technology.

DVD-RAM wheels can be used to record and play streaming video on hardware supporting DVD-VR specification (see below).

W DVD + RW (Digital Versatile Disc Rewritable)

The DVD + RW format is progressing only by its developers - Hewlett-Packard, Mitsubishi Chemical, Philips, Ricoh, Sony and Yamaha (not supported by the DVD forum).

On DVD + RW drives, you can write both streaming video or sound and computer data. DVD + RW discs can be overwritten about 1000 times.

The DVD + RW database has created a streaming video recording format - DVD + RW Video Format. Devices and discs operating in this format are positioned in the market as fully compatible with equipment operating in DVD-Video formats. This means that DVD + RW discs containing video materials can be played on a previously released DVD household apparatus.

Philips announced the start of the release of its DVD video recorder in September 2001 DVD + RW discs recorded on this device are also read by conventional DVD-Video players. This decision was proposed as a response step on the DVD adopted DVD specification of the DVD-VR (see below).

W DVD-RW (Digital Versatile Disc Rerecordable)

There are other names of this format: DVD-R / W and less often DVD-ER.

DVD-RW - multiple format developed by Pioneer. DVD-RW discs contain 4.7 GB to one side, are available in one-sided and double-sided modifications and can be used to store video, audio and other data.

DVD-RW discs can be overwritten up to 1000 times. Unlike DVD + RW and DVD-RAM formats, DVD-RW discs can be read on the first generation DVD-ROM drives.

TDK declares that the durability of the DVD-RW discs produced by it is about 100 years.

  • · DVD formats for one-time recording
  • W DVD-R (Digital Versatile Disc Recordable)

DVD-R is a format of a single record developed by Pioneer. Devices based on this format were the first to be recorded on DVDs. The technology of recording is similar to those used in CD-R and is based on an irreversible change under the influence of the laser of the spectral characteristics of the information layer, covered with a special organic composition.

DVD-R discs can be recorded both computer data, multimedia programs and video / audio information. Depending on the type of recorded information, discs can be read on other compatible with the recorded device types, including DVD-Video video players and most DVD-ROM drives. Unilateral DVD-R discs accommodate 4.7 or 3.95 GB to the side. Double-sided discs are available only to a total capacity of 9.4 GB (4.7 GB to the side). Currently, the format does not support recording technology in two layers.

DVD-R disk durability is estimated for more than 100 years. To protect against illegal copying, two specifications have been developed: DVD-R (A) and DVD-R (G). Two these versions of one specification use a different laser wavelength during information recording. Thus, discs can only be recorded on their appropriate equipment specifications. Playback of discs can be performed equally successfully on any equipment that supports DVD-R format.

DVD-R (A) (DVD-R for Authoring) is used in professional applications. In particular, the support of a special format (Cutting Master Format) allows you to apply these disks to record the source replica of information (premastering) instead of normal use for these purposes DLT tapes.

DVD-R (G) (DVD-R for General) is designed for wider use. Disks of this format are protected from the possibility of beaten copying information from other disks. The format is supported in mass storage devices (for example, in robotic DVD libraries offered by Pioneer itself).

The DVD-VR specification is based on DVD-RAM and supported by the DVD forum. The DVD-VR format allows you to record in real time up to 2 hours of high-quality video in MPEG-2 format to a single-sided DVD-RAM disk with a capacity of 4.7 GB and provides features such as editing already recorded video materials, record various types of static images. Electronics based on this format is released, for example, Panasonic, Toshiba, Samsung, Hitachi.

Topic number 2. Technical storage facilities

purpose: Give basic concepts on the physical and logical organization of data storage on a personal computer.

Learning tasks:Acquaintance with internal and external computers devices, basic tools for storing documents.

The main issues of the topic:

1. Basic devices used for long-term data storage on PC.

2. Logic organization of storage of data on magnetic disks.

3. Physical organization of data storage on magnetic disks.

Training and teaching methods:seminar

Theoretical block

Basic devices used for long-term data storage on PC

The devices used to store information on the PC relate to the external and very diverse in design. If you use the type of media as a classification feature (medium - a material object capable of storing information) used to store information, they can be divided into the following conditional categories.

Ribbon type devices are called - strides.

Disk devices include - magnetic: hard magnetic discs (hard drives), flexible magnetic discs; Optical: CD-ROM CD players, etc.

Consider disk devices in detail.

Magnetic discs relate to magnetic information media. As a storage medium, they use magnetic materials with special properties that allow to fix two magnetic states - two directions of magnetization. Each of these states are put in line with binary numbers: 0 and 1. Read the magnetic states from the disk is made by a special head. Magnetic discs The most widespread information storage devices on the PC. Devices for reading and writing information on a magnetic disk is called a drive.

Consider the drives of flexible magnetic disks.

On a flexible magnetic disk, the magnetic layer is applied to the flexible basis. In size, flexible magnetic discs (flop) are two species 3.5 "and 5.25". Depending on the number of parties, the diskettes used for recording, and the density of the same side records they have the following labeling and container:



DS / DD-double-sided (Double Sides), single density (Single Density), 360 KB.

DS / DD-double-sided (double sides), double density (double density), 720 kb.

DS / HD-bilateral (Double Sides), high density (high density), 1440 KB.

To make a floppy disk, it must be formatted. Formatting a floppy disk is the process of recording on its surface of special marks of determining the location of information records on disk and sections are not suitable for recording, as well as other managing information.

Storage devices on hard magnetic disks or hard drives.

Reference to the main devices in the PC for long-term storage of information.
The name "Winchester" occurred by chance that the labeling of the first drives coincided with the marking of the carbar of the Winchester system 30/30 very popular in America. Constructively "Wincher" is a sealed metal case, in which the block controlling the electronics drive is located, and a set of several discs made of aluminum or ceramics and a layer coated with a magnetic material located on one rotating axis, which is driven by the electric motor, and also Block reading heads.

SCSI interface (Small Computer Systems Interface). Basic interface of small computer systems. Allows you to connect up to 7 devices of various types: "Winchesters"; Scanners, etc. The data transfer rate ranges in the range of 1.5-5 MB / s. The hardware is implemented for use in the PC in the form of an additional adapter inserted into the Slot of the Empathy of the Motherboard. There is an upgraded version of SCSI - SCSI-2, depending on the modification, the data transfer rate is increased to 20-40 MB / s ..

IDE-ATA interface (Integrated Drive Electronics - AT Attachment)

Created in 1984 on the basis of SCSI in order to simplify and reduce the latter. It is distinguished by the fact that the electronics control interface is not on a separate adapter, but is located in the hard disk housing and on the PC motherboard. The maximum number of connected devices to 4. It has several upgraded variants of the maximum capacity of the drives used and the data transfer rate:

EIDE or ATA-2 is supported by a capacity of more than 540 MB. Maximum theoretical transmission rate 11.1-16.6 MB / s.

ATA-3 or UDMA-33 increased the reliability of drives (SMART-Self Monitoring Analyses and Report Technology technology - technology of self-tracking, analysis and report, allowing drives to inform the system about their faults and eliminate them). The theoretical data transfer rate is increased to 33 MB / s. The EIDE interface has become standard for PC.

Media storage media

Flesh - Memory - small-sized external memory, 128 MB to 4 GB, connected to a computer via USB - port.

In order to store information for long-term time and transfer from one data media to another, devices on hard drives, DVD, CD-equipment, flash drives, drives on flexible disks are used.

Winchester is a means of constant saving information, programs in the computer.

Flexible magnetic disk is the principle of data recording on magnetic tapes. Such a device can accommodate information up to 600 pages of a text document.

CD is the principle of an optical record. You can write even the encyclopedia that contains many volumes. Flash memory is a device that does not need food from electricity.

Many are thinking: what does it serve for long-term storage of information? So, the structure of my story is as follows:

  1. what serves for long-term storage of information;
  2. types of information.

What serves for long-term storage of information

The main information process is the process of saving information, that is, a method, due to which it is possible to transmit data on space and time. In order to save information, devices or devices that depend on the type of stored information are used. In order to ensure the ordering of this process, the availability of information systems equipped with a search procedure, placement, as well as editing information. Main distinctive feature of information systems - data Key procedures.

Programmers are determined by: in order to save information, external storage devices should be used. It can be a drive or a carrier of all sorts of types, which may be imagined to yourself.

Types of information

In addition to the foregoing, it should be said about what information types are. So information may be as follows:

  • textual;
  • visual;
  • numerical;
  • sound recorder;
  • video.

The most common in today the method of saving information is the text type. True, this storage method is not reliable and durable. Graphic, or the pictorial type - the most ancient storage method of information, these are all sorts of schemes, graphics and drawings.

External memory is used for long-term storage of information solid media storage drives on rigid magnetic disks (HDD, HDD) hardware implementation of magnetic tape drives - "Streamers" drives on laser disks (CD, Compact Disk, etc.) Media information - Wednesday Recording / reading and storing information.

Option of the classification of information media used in computer equipment Media information for computers Ribbon carriers Magnetic disk carriers Optical Flash carriers magneto optical

The main type of external memory is the magnetic memory Magnetic recording at the end of 1898 Dane Valdemar Polesen (Valdemar Poulsen) suggested a device for a magnetic sound recording on steel wire. After 30 years, the German engineer Fritz Pleimer (Fritz Pfleumer) presented a sound recording device with a carrier in the form of a paper tape, which caused a thin steel coating. In 1932, the German company AEG demonstrated the first recording apparatus, which was called "Magnetophon". The magnetic tape has the main disadvantage - the ability to demagnetize during long-term storage and has an uneven frequency response (different sensitivity to record at different frequencies). In addition, any magnetic tape has its own noise (the physical properties of the magnetic layer and the methods of recording-play sound).

The principle of the magnetic record consists in the effects of the electromagnetic field on the ferromagnetic material of the magnetic tape, carried out when recording, as well as overwriting an analog signal. The magnetic field in the recording process varies in accordance with the changes in the electrical signals. Electrical oscillations from the sound source are fed to the recording head and excit the magnetic field of the sound frequency (20 Hz - 20 k. Hz). Under the action of this field, there is a magnetization of individual sections of the magnetic tape, evenly moved along the recording heads, erasing and playback (Fig.).

To record playback, as well as the use of various data on computer-readable data media, use analog (sound and video) signal to digital form. Such a technology was named the digitization of information. The principle of digitization (encoding) of the sound is to convert continuous different over the amplitude of the amplitude audio and video signals into the encoded sequence of numbers representing the discrete values \u200b\u200bof the amplitudes of this signal, taken after a certain period of time. To do this, it is necessary to measure the amplitude of the signal at certain intervals and at each time of the segment to determine the average amplitude of the signal. According to the Shanon Theorem (Kotelnikov), this period of time (frequency) should be no less than the twice the maximum frequency of the transmitted beep (Fig.).

This frequency is called the sampling frequency. Discretization is the process of taking the references of the signal continuous in time in equivalent from each other by the time of points constituting the sampling interval. During the sampling process, the level of analog signal is measured and remembered. Amplitude frequency (Hz) Fig. 13. Convert analog signal into digital. The less often (less) time intervals, the quality of the encoded signal is higher.

Streamers Tape media are used to back up in order to ensure the safety of data. As such devices, a streamer is used (Fig.), And the carrier of information in them is used magnetic tapes in cassettes and tape cartridges. Usually, the recording is carried out to the magnetic tape, while the domain corresponds to a binary unit. If the reader does not detect it, the value obtained corresponds to zero.

The record system for magnetic discs and diskettes are somewhat similar to the record of the record on the record. Unlike the latter, the record is not carried out on the helix, but on the concentric circles - tracks ("Tracts" - Traks) located on two sides of the disk and forming cylinders. Circle, in turn, are divided into sectors (Fig.). Each floppy sector, regardless of the size of the track, has the same size equal to 512 bytes, which is achieved by different recording density: less peripherals and more closer to the center of the floppy disk.

Magneto optical information carrier External high-spirits and storage devices. Magneto-optical disks (MO) appeared in 1988. The monitor is enclosed in a plastic envelope (cartridge) and is an arbitrary access device. It combines the magnetic and optical principles of storage of information and represents a polycarbonate substrate (layer) with a thickness of 1, 2 mm, which causes several thin-film magnetic layers (Fig.). Recording a laser with a temperature of about 200 o. The magnetic layer occurs simultaneously with the change in the magnetic field. Fig. The composition of the Disk.

Data recording is carried out by a laser in a magnetic layer. Under the influence of temperature at the heating site in the magnetic layer, the resistance to the change in polarity is reduced, and the magnetic field changes the polarity at a heated point to the corresponding binary unit. At the end of heating, the resistance increases, but the installed polarity is preserved. Erasing creates the same polarity in a magnetic field corresponding to binary zeros. In this case, the laser beam consistently heats the washed plot. Reading recorded data into the layer is produced by a laser with a smaller intensity that does not lead to the heating of the readable area. At the same time, in contrast to CDs, the disc surface is not deformed.

Compact optical disk (CD) is a plastic disk with a special coating on which recorded information is in digital form. Due to the change in the speed of its rotation, the track relative to the reading beam of the laser moves with a constant linear speed. At the center of the disk the speed is higher, and the edge is slower (1, 2- 1, 4 m / s). The CD use a laser with a radiation wavelength \u003d 0, 78 microns. The "burnable" laser digital information is preserved in the form of "pit" - cigroxks width 0, 6-0, 8 μm and a length of 0, 9-3, 3 μm. There are three main types of CD: ● CD-ROM to which the entry, as a rule, is carried out by the factory method of stamping from the matrix; ● CD-Rs used for one or non-slip laser recording sessions; ● CD-RW intended for multiple recording cycles.

In the CD-R (Compact Disk Recordable) on top of the reflective layer of gold, silver or aluminum, there is an organic layer of special light-melting plastic. In view of this, such a disk is sensitive to heating and exposure to direct sunlight. In CD-RW, an organic composition is also used as an intermediate layer, but it is capable of moving from a crystalline (transparent for laser) in amorphous with a strong heating. Weak heating returns it back to the crystalline state. Thus, overwriting is carried out.

DVD In early 1997, a CD standard called DVD (Digital Video Disc) appeared, designed mainly to record high-quality video programs. In the future, the DVD abbreviation received the following value - Digital Versatile Disc (universal digital disc), as more fully meets the capabilities of these disks to write sound, video, textual information, PC software, etc. DVD provides higher image quality than CD. They use a laser with a shorter radiation wavelength \u003d 0, 635-0, 66 μm. This allows you to increase the record density, i.e. reduce the geometric sizes of PIT up to 0, 15 μm and the pathway up to 0, 74 μm.

The density of the optical disc recording is determined by the laser wavelength length, that is, the possibility to focus on the disc surface of the beam with a stain, the diameter of which is equal to the wavelength. Following the DVD, at the end of 2001, Blu-ray devices appeared, allowing to operate in the blue region of the spectrum with a wavelength \u003d 450-400 nm.

Fluorescent Multilayer Disk (Fluorescent Multilayer Disk) is used to increase the tank. The principle of their action consisting in changing the physical properties (the appearance of fluorescent luminescence) of some chemicals under the influence of the laser beam (Fig.). Here, instead of CD and DVD technologies using a reflected signal, the light is lowered by the light to the laser, the light is emulsioned. Such discs are made of transparent photochromas. Under the influence of laser radiation, they include a chemical reaction, and individual sections of the information layer ("Petes") are filled with fluorescent material. This method can be considered by the method of data recording. In the greater degree, such a record is possible when using three-dimensional holography, which is now in a crystal size with a sugar cube, to accommodate up to 1 TB of data.

Two main types of Flash memory are used: NAND and NOR (logical or-no) and Nand (logical function and non). The NOR structure consists of parallel enabled elementary storage cells. Such the organization of the cells provides random access to the data and the delete record of information. The NAND structure is based on the principle of a serial connection of elementary cells forming groups (16 cells in one group), which are combined into pages, and pages in blocks. With such a construction array, an appeal to individual cells is impossible. Programming is performed simultaneously only within one page, and when erasing, the circulation occurs to blocks or block groups.

NOR chips work well jointly with RAM RAM, so more often used for BIOS. When working with relatively large data arrays, recording / erasing processes in the NAND memory are performed much faster than in the NOR memory. Since the 16 adjacent Nand memory cells are connected in series, without contact gaps, a high density of cell location on a crystal is achieved, which makes it possible to obtain a large container with the same technological standards. From the mid-1990s. NAND microcircuits appeared in the form of solid-state disks (SOLID STATE DISK, SSD). To compare the access time in the SDRAM it is 10-50 μs, the flash memory is 50-100 μs, and the hard drives - 5000 - 10,000 μs.

Salted Samsung hard drive. The speed of reading from such a disc is 57 MB / s, and the recording speed is 32 MB / s. SSD power consumption is less than 5% of the indicators of traditional hard drives, increasing by more than 10% of the battery life of portable PCs. SSD provide ultra-high reliability of data storage and have proven itself in extreme temperatures and humidity conditions. Petersburg firm "Just. Soft "offered Flash driver. RAID to combine two flash drives in a RAID array.

Flash memory is a portable non-volatile drive. The following Flash Memory Standards are commonly used: Compact. Flash, Smart. Media, Memory Stick, Floppy disks, Multi. Media Cards, etc. They can be used instead of floppy disk, laser and magneto-optical compact, small hard drives. Modern interchangeable flash memory devices provide high data exchange rate (Ultra High Speed) - more than 16, 5 Mbps. To connect to the USB port of the computer, special USB Flash Drive is used (Fig.), Which are mobile small-sized storage devices that do not have mobile and rotating mechanical parts.

Holography is a photographic method of recording, playback and conversion of wave fields. For the first time he was proposed in 1947 by the Hungarian physicist Dennis Gabor. In 1960, with the advent of the laser, it was possible to accurately record and reproduce the volume images in the Lithium Niobate crystal. Since the 1980s, with the advent of CDs, holographic information storage devices based on laser optics have become one of the external memory technologies. Holographic memory represents the entire volume of storage medium of the medium, and the data elements accumulate and read in parallel.

Modern holographic storage devices were called HDSS (Holographic Data Storage System). They contain: laser, beam discriminator for separating a laser beam, mirrors for the direction of laser rays, a liquid crystal panel used as a spatial light modulator, lenses for focusing laser rays, a lithium niobate crystal or a photopolymer as a storage device, a photodetector for reading information (Fig.) .

With the advent of computers, the issue of storing information was very sharply staging, which was originally fed digitally. And now this problem is very relevant, because the same photos or videos want to save for a long memory. That is why it will be initially necessary to find the answer to the question of, for long-term storage of information, which devices and carriers are served. Also should fully appreciate all their advantages and disadvantages.

The concept of information and methods for its storage

Nowadays, you can find several basic types of information data on computers. The most common forms are text, graphic, audio, video, mathematical and other formats.

In the simplest version, hard disks of computers are served to store information to which the user saves the file initially. But this is only one side of the medal, because in order to view this information (extract), you need at least the operating system and the relevant programs that by and large are information data.

Interestingly, in schools in informatics lessons, when choosing the right answer, such questions are often found, the statement is often found that, they say, the RAM is served for long-term storage. And schoolchildren who are not familiar with the specifics and principles of her work, consider it the right answer.

Unfortunately, they are mistaken, since only information about the processes running at the moment is currently stored, and when they are completed or rebooting the system, the RAM is fully cleaned. It looks like the principle of the operation of once popular children's toys for drawing, when on the screen you could first draw something, and then shake the toy, and the drawing disappeared, or when the teacher erases with the blackboard text written by chalk with the blackboard.

How information remained earlier

The very first method of preserving information in the form of rock paintings (by the way, graphics) is known since time immemorial.

Much later with the advent of speech, the preservation of information has become a process, so to speak, transmission from mouth to mouth (myths, legends, epics). Writing led to the fact that books began to appear. Pictures or pictures were not forgotten. With the advent of photography photos, sound recordings and video, the corresponding media appeared on the information field. But all this turned out to be short-lived.

Device for long-term storage of information: basic requirements

As for computer systems, it should be clearly understood that modern carriers must be complied with that the information is kept for them as long as possible.

The most important requirement is durability and resistance to wear and physical or other damage. And in relation to any type of carrier on time intervals, you can speak very relatively, because, as you know, "nothing is always under the moon."

For long-term storage of information, what carriers are

We now turn directly to devices on which any type of data can be stored, if not forever, then at least long enough. So, for long-term storage of information serve what types of storage?

Among the most commonly used in relation to computer technicians are allocated as follows:

  • domestic and removable hard and zip-disks of computers;
  • optical CDs, DVD- and Blu-Ray carriers;
  • flash memory of any type;
  • dakes (now used extremely rarely).

Benefits and disadvantages of carriers

As can be seen from the list, only the hard drives are built into computers relate to internal storage devices. All other carriers are external.

But all of them are one of them are susceptible to aging or external influences. In this sense, the floppy disk or the same CDs or carriers of another format are the most unsafe, although optical media in this regard look more wear-resistant. But how much can they serve? 5-10 years old? But if the information on them is stored, viewing very often, the service life is reduced.

Flash drives and hard drives have more long-term exploitation, but they are not insured against wear, damage and aging.

Winchesters begin to "draw" (this is a natural process), flash drives can be exposed to the same sunlight, moisture, or even delete data when extracting or software failures. In addition, there are many more additional factors that can lead to the inoperability of devices.

Nevertheless, speaking that for long-term storage of information, the devices listed in the list should be borne in mind that such a classification is provided solely for the current state of affairs in the computer world. Who knows, maybe even in the already foreseeable future, completely new carriers using other technologies will be invented, because it is alleged, the creation of quantum computers is not far off.