In the constant pursuit of gigahertz and gigabit per second, which the CPU passes through, we very often forget that the computer has many other important components that need improvement, such as RAM, as well as drives that store processed data. The development of devices to store information is just as important as increasing the computing power of the CPU. In this article, we will talk about the prospects facing modern storage media, such as hard disks.
In the second part of the article we will describe the future of optical disk drives, in the third we will try to consider some of the most interesting and fundamentally new developments in the field of microelectronic mechanical systems, which may be used in devices that replaced the traditional HDD and less traditional, but completely familiar CDs, DVDs, and BlueRay.
In order to be able to compare various types of media with each other, it is necessary to highlight some characteristics inherent in each of them. Such as, for example, the speed of reading or writing, the average search time of an arbitrary data element (Random Seek), as well as the cost of storing a unit of data. If we want to compare data storage devices that are not yet in nature, but they will be born in the future, then we need to try to break them down into three large groups: those that are about to begin to be produced and will soon appear on the market; those that will become widespread in a more or less foreseeable future and, finally, those that will appear only under favorable circumstances and the successful completion of all research related to their implementation. In fact, it is difficult to compare a modern hard drive with a random access time of 9.0 ms with any drive of the distant future, which will have the same characteristic several orders of magnitude better (i.e., less), but which is not yet on store shelves and isn’t will be in the next fifty years. Naturally, they continue to make such comparisons on the Internet, forgetting that the prototype that appeared in the top-secret laboratory of Silicon Valley and works only at a temperature close to absolute zero is not the same as the hard drive that is on your computer the desktop.
Trends in the development of magnetic storage devices
Let's start with hard drives, because today this is perhaps the most common and popular type of drive, and in the next 3-4 years, the hard drives will probably not have to test the competition from other types of drives. Opponents so far clearly lose either in speed, or in capacity, or in cost, and most often - in several indicators at once.
What is a Winchester today, we all know well: capacity - say, from 20 to 400 gigabytes, average search time - from 8 to 12 ms, sequential read / write speed - 30-40 Mb / s. In principle, the characteristics are not bad, although, again, depending on what to compare: the RAM will work faster (but it turns out to be more expensive, moreover, when it is turned off from the network, it completely “forgets” everything that was written to it, - agree, a significant drawback); rewritable DVDs are much cheaper (but they didn’t lie close by the speed of work, and their capacity is relatively small).
If you recall how much data you have to read and write to the hard drive when working with multimedia, as well as the fact that most modern operating systems use it in one way or another as an addition to random access memorywriting a swap file there, it becomes obvious that no matter how good the characteristics of the hard drives are, it would be nice to improve them. First of all, manufacturers would like to increase the mentioned read / write and search speed, as well as capacity. In second place are the dimensions, as well as power consumption and shock resistance, coupled with reliability. Naturally, in future models of hard drives, these characteristics will be necessarily improved, only questions remain: how and when?
There are two ways to achieve an increase in the reading speed: either by increasing the recording density of information, or by making the “pancakes” of the hard drive rotate at a higher speed. Both methods have their drawbacks. As the spindle speed increases, the hard drives start to warm up much more strongly and become noisier, not to mention the fact that the material of which the plates are made must be strong enough to withstand the corresponding mechanical stresses and not be deformed. The technology of their manufacture becomes more complicated, and this affects their cost: it is significantly higher. But in addition to increasing the linear reading speed, the average search time also decreases - due to the fact that the head is earlier above the desired sector of the track. The problem with excessive friction and noise will be partially helped by hydrodynamic bearings, which some manufacturers have recently started to use, but still it seems to us unlikely that the spindle speed in 3.5 "winches can exceed 15-20 thousand revolutions per minute, whatever "tricky" and "sophisticated" bearings were not used.
With an increase in recording density, negative side effects are also observed, but it is still easier to deal with them. But the pluses include an increase in drive capacity, and this is much more important parameter for manufacturers of hard drives than the average search time. After all, the average buyer pays more attention to him. Therefore, manufacturers of hard drives most often try to improve their products in this way.
Super Paramagnetic Limit
Obstruction in achieving ultra-high recording density
The plate of a modern hard disk consists of a glass or aluminum substrate coated with a magnetic coating on top. Individual sections of this coating can be magnetized by one of two possible wayswhich denote zero and one (i.e. 1 byte). Such a magnetized area is called a magnetic domain, and is a miniature magnet with a specific orientation of the south and north magnetic poles. If you set the magnetization of the domain, information will be recorded. Ultimately, the recording density of information determines the size of this domain itself. It would seem that reduce the size of domains for health, and the hard drives will be as capacious as you can imagine, but not everything is so simple.
Those of us who have not forgotten school physics can strain and remember that all substances are divided into paramagnetic, diamagnetic and ferromagnetic. Diamagnetic are those substances that, being outside a magnetic field, do not have magnetic properties - it is clear that they are not suitable for creating information storage devices. Atoms and molecules of paramagnetic substances, on the contrary, by themselves, even before an external magnetic field began to act on them, are elementary magnets - however, they are also not very suitable for creating storage rings. And only ferromagnets in which magnetic grains of a sufficiently large size act as elementary magnets are suitable for long-term storage of information.
To record one bit of information, the head of the hard drive creates a directional magnetic field in a certain way, which orientates all elementary magnets of the domain mainly in one direction. This orientation is safely maintained for a long time after the head ceases to affect the ferromagnet. However, even after repeated recording in the domain, there always remain such magnetic grains whose magnetic orientation does not coincide with the orientation of the entire domain; moreover, the relative content of "bad" grains is greater, the less grains in the domain, that is, the smaller its size. If you try to make the domain too small, the relative number of "bad" grains will be so large that the information signal can no longer be distinguished from the noise. There are two ways out of this situation: the search for new paramagnetic materials with small and predominantly homogeneous magnetic grains and the development of algorithms that allow us to select a useful signal even with a low signal-to-noise ratio. However, here there is its limit of possibilities. If the magnetic grain is too small, then the thermal energy of the environment is more than enough to spontaneously change its magnetization. Roughly speaking, in this case we will get a substance that is very close in paramagnetic property - hard drives made from such materials can only work when cooled with liquid nitrogen or, even worse, with liquid helium. Because of this quasi-transition of the ferromagnetic substance into the paramagnetic described limitation, it is called the superparamagnetic limit.
Well, in addition to the purely physical limitation in the form of a superparamagnetic limit, there is also a technical one related to the process of writing and reading information, for which, as already mentioned, a special head is used. In the very first models of hard drives, the head was universal - the same tiny inductor was used both for reading and writing information. Modern heads consist of two parts: recording (inductor) and reading (magnetoresistive head, which changes its resistance depending on the magnetic field). Naturally, the size of the head is finite, and today it is they who largely determine the size of the minimum magnetized area - the domain. However, in modern hard drives, the domain size is so small that to further reduce it, manufacturers will need to step over the superparamagnetic limit.
That is why specialists from leading companies developing hard drives have long been struggling with the problem, and I must say, very successfully. The development paths of technologies and their own know-how, which allow overcoming the superparamagnetic limit in the future, have been developed by each of them. Moreover, some are already used in serial production of hard drives, some are used only in prototypes, but from day to day they will be used in assembly-line assembly, some may never get to mass use.
Afc
Perhaps the first sign that foreshadowed an imminent victory over the superparamagnetic limit was the technology for creating magnetically compensated films, proposed by IBM. The essence of the idea is to apply a three-layer antiferromagnetic coating on the hard drive’s disk called AFC (antiferromagnetically-coupled, antiferromagnetic pair), in which the pair of magnetic layers is separated by a special insulating layer of ruthenium.
Due to the fact that the magnetic domains located under each other have an antiparallel orientation of the magnetic field, they form a pair that is more resistant to spontaneous magnetization reversal than a single “flat” domain. Trial batches of hard drives using AFC technology appeared in 2001, but its mass use has only begun now. However, AFC is not an absolute panacea - it is only a small improvement of the old technology, which allows increasing the capacity of hard drives by 4-8 times, but not more.
PMR
Significantly greater gains promise the use of perpendicular recording (PMR, Perpendicular Magnetic Recording). This technology has been known for a long time, it was actively studied already 20-30 years ago, but then it did not work to bring the matter to a working and inexpensive device in production. Now they have recalled PMR, Seagate has been very fruitful in developing new hard drives based on this technology. In August 2002, in Pittsburgh (USA), she organized a special research center, whose plans included a thorough study of not only PMR, but also other problems associated with the creation of promising information storage media on magnetic media. As the name implies, PMR, in contrast to the classical recording technology, uses magnetic domains with a perpendicular (rather than parallel to the surface of the disk) magnetic field.
This allows you to reduce the longitudinal dimensions of the domain, while slightly increasing its height. In addition, in the case of PMR, the neighboring invert bits (1 and 0) no longer look at each other with the same poles, which, as you know, repel each other - this allows you to reduce the size of the interdomain space compared to the classical recording technology, which further increases the capacity Winchesters.
It is clear that for the implementation of PMR it is necessary to apply both a completely different design of the read / write head and a new structure of the magnetic surface of the disk. The PMR recording head should have only one main pole of the core, the second pole will be auxiliary. The main pole of the core creates a strong magnetic field, the lines of which extend perpendicular to the magnetic surface of the disk; passing through a special inner magnetic layer, they close at the wide auxiliary pole of the core. Naturally, the field with the largest magnitude will be at the main pole - the magnetization reversal will take place there, at the wide auxiliary pole the field will be too weak to affect the surface of the disc, and it will remain unchanged during recording. Like AFC, PMR is a ready-to-use technology for mass production. The hard drives using it should appear, if not in this, then in the next 2005.
HAMR and SOMA - 2010 Technologies
Among the most promising technologies of the future, the task of which is to supplement PMR when it has exhausted its resources and approaches the next limit, we can include thermomagnetic recording (HAMR, Heat Assistant Magnetic Recording) and self-organizing magnetic gratings (SOMA, Self-Organized Magnetic Array) . Dieter Weller, director of the media research division at Seagate, believes that HAMR will once again change the way data is read and written, and SOMA is the process of manufacturing magnetic sputtering for discs.
A feature of HAMR is the use of magnetic materials with a high coercive force, which provide high thermal stability of the recorded surface areas. To record information, the magnetic domain is preheated using a focused laser beam. The beam diameter determines the size of the region corresponding to one bit of information. With an increase in the temperature of the domain, a significant change in its magnetic properties occurs (the coercive force decreases), and, thus, the heated areas become capable of magnetization. Naturally, for introducing HAMR into mass production, it is necessary to solve many problems, such as the development of inexpensive and miniature lasers with a very small wavelength (otherwise it would be impossible to create a focusing system), it is also necessary to provide efficient heat removal from the plates (remember how modern hard drives are heated, what will happen if they are also heated with a laser, like food in a microwave ?!) and a number of others. However, the fact that Seagate specialists have already assembled a working experimental setup that implements recording using HAMR technology suggests that these problems will most likely be successfully resolved. The company promises that HAMR will be used in commercial products as early as 2010.
Nevertheless, as already mentioned, to further increase the recording density, it is also necessary to change the manufacturing technology of the magnetic disks themselves, achieving uniformity and uniformity of the layer of particles that make up its surface. If this is not done, then neither HAMR nor any other tricks with a recording head will help. The modernization of reading / writing mechanisms should go hand in hand with the improvement of materials and the quality of the deposition of the magnetic layer. Here, experts see a way out in using the already mentioned SOMA technology, which provides for the formation of a monodisperse layer of “self-organizing magnetic arrays” on the disk surface from tiny homogeneous iron-platinum conglomerates about 3 nm in size (3 nm are 10-15 solid atoms laid out in a row )
The use of this "nanotechnology" will significantly reduce the level of instability of individual magnetic grains and reduce the size of the magnetized region for recording data bits. Seagate believes that all this can allow producing drives with a capacity of tens, or maybe even hundreds of terabytes. And this will happen not in the transcendental future, but by the beginning of the next decade.
Instead of a conclusion
As we can see, improving hard drives on their way to reaching the superparamagnetic limit can lead to the fact that they will absorb some of the properties of their closest competitors - optical storage media, such as CDs and DVDs. Naturally, all this will lead to a sharp increase in their complexity, and hence cost. At the same time, devoid of any superparamagnetic limits, optical devices will develop, capturing more and more new frontiers, gaining next victories, and will probably surpass all major characteristics in ten to fifteen years magnetic drives. In the second part of the article, we will try to deal with the future of CDs and DVDs, as well as their many modifications and successors.
Practice Plan 17
Subject: Storage media
Purpose: to study the typology of storage media and the physical basis of recording digital information
Time: 4 hours
Questions:
1. The physical basis of recording digital information.
2. HDD. Physical media information.
3. Compact optical discs.
4. Portable storage media
Execution technique:
Physical Basics of Digital Information Recording
At first, it was quite significant to divide the possible carriers of digital information into stationary and portable devices (in this case, it would be more correct to use direct translation - portable). For systems of personal computers of both types - IBM PC or Macintosh, the main stationary storage medium was and remains the hard drive.
Portable devices developed and transformed very quickly. First-time standard floppy disks with a diameter of five inches with a quarter and a capacity of several hundred kilobytes (up to 360) are no longer used, and it will be quite difficult to find equipment for reading information recorded at one time on them. Three-and-a-half-inch standard disks with a capacity of 1.44 MB, which have replaced, are also gradually becoming obsolete. New computers often no longer have the appropriate drives. Subsequently came the recordable optical CDs - CD-R or CD-RW, DVD-R. DVD-RW, as well as devices that do not contain rotating parts - FlashJet and the like, compatible with universal uSB ports. I must say that the development of compact memory devices was greatly influenced by the introduction of music standards, digital video and cameras.
To record characters of machine-readable information, changes in various physical parameters are used, for example:
End-to-end permeability (perforated cards);
Reflectivity (optical CD-ROMs. All printed and handwritten products, excluding Braille):
Changes in electrical conductivity (open or closed position of the transistor);
Magnetization changes (magnetic tapes, disks);
Changes in quantum parameters:
Sequence of convex points (Braille texts);
In accordance with the parameters of the physical environment, recording and reading information are different; magnetic media, optical media, mixed magneto-optical media, memory cards - microcircuits.
The most common geometric shape of the media:
Disks (one-sided and two-sided);
Flat memory cards - microcircuits (chips);
Separate portable devices.
HDD. Physical storage media
This is a common physical medium in the server and in personal computer. A hard drive, sometimes called a “hard drive," consists of a set of flat disks rotating on the same axis with a diameter of several centimeters (a typical diameter is from three and a half inches or less), coated with a magnetic layer. The operational properties of a hard disk are very attractive: high capacity, quick access to recorded information, high speed of reading information and interchangeability (standardization of disks). Fast access information is provided by the small distance that the read head passes when searching for the right place, as well as by writing information to previously created (formatted) sectors on the disk. Technical features that ensure low wear of the read heads and the magnetic layer of the plate surface — non-contact reading of information, “flight” of the head above the disk. Special measures are being taken to ensure the reliability of the support bearings of the hard drive, for example, gas-dynamic bearings are used, that is, there is also a “flight” mode above the support surface. Therefore, to ensure the server resource, it is dangerous not the number of hours worked, but the number of on / off switches associated with the “landing” of heads and acceleration of disks. The indicated design feature of the disk makes it possible (in the presence of uninterruptible power supply devices) to leave the server turned on for many days (weeks). Thus, one of the significant advantages of the electronic library is achieved - customer service 24 hours a day all year round. Sample hard drive settings.
1. Seagate Technology, Barracuda 7200 family of hard drives, 160/120/80/40 GB capacity, with Serial ATA interface. average search time 8.5 ms; one of the latest developments is the Barracuda NL35 hard drive. memory capacity of 500 GB, 3 plates, plate rotation speed of 7200 rpm. The data reading speed is 47 Mb / s. Another example of the products of the same company is the Cheethah family of disks with a disk rotation speed of 15 thousand revolutions per minute, with a memory of up to 300 GB.
2. Meets the highest requirements of reliability, noiseless and shockproof Samsung hard drive with a capacity of 40.8 GB; the speed of rotation of a package of 2 disks 5400 rpm; buffer capacity 512 Kb, average access time 8.5 ms, data transfer rate up to 66 Mbps. The average time between failures is 500 thousand hours (approximately 57 years), the unit cost of data storage is $ 1 per 200 Mb. that is, 0.5 cents for I Mb.
3. The same principle of ensuring high reliability is realized by the design of Western Digital WD Caviar hard drive for servers with a capacity of up to 250 GB, which has a special function of reliability control and prevention of disk failure. The estimated time between failures is 1 million hours (over 100 years).
To store large data arrays, there are special disk systems with high speed, for example, a digital storage library (structurally - one cabinet) from 73 GB disks each, with a total capacity of 9 TB, goes on sale.
In the standby position and in operation, the disk is in a state of uniform, continuous and rapid rotation. Access to the recorded information occurs due to the transverse movement of the heads over a very short distance. The load on the physical basis of the carrier (created by centrifugal force) is constant at all times.
Information carriers on magnetic tapes.These media are less commonly used today than at the dawn of the computer era. Nevertheless, their advantages are obvious: they are well-developed production technologies, high recording density, high speed of reading information and large capacity. However, the structural difference between tape devices compared to hard drives in kinematics is absolutely fundamental.
The standby state is a fixed tape.
Exit to the starting position when searching for a file in a certain and previously unknown section of the tape is accelerated movement (rewind) and subsequent sharp braking.
The operating mode of reading or writing is the uniform movement of the tape at a speed much slower than when searching.
Tape devices do not use monotonous, but "torn", pulsating operation, with a large and time-varying mechanical load on the physical basis of the information carrier. An irreparable drawback of devices using magnetic tapes is a long time for access to information, the gradual erasure of the magnetic layer, deterioration of the record due to demagnetization of the tape, stretching of the base tape during operation. Nevertheless, digital storage devices are very often implemented on magnetic tapes, for example, tape drives, digital tape recorders DAT (Digital Audio Tare), tape recorders with a spiral track recording, occupying the entire width of the magnetic tape (Exabyte).
Some examples of information storage devices are Surestore tape drives with DLT (Digital Linear Tare) technology, which use 160 GB cassettes each, data transfer speeds of 16 Mbps (384 tracks, average file access time of about 70 s). To illustrate the wide distribution of these systems, we indicate that by 2002 2 million drives and 80 million cartridges were sold.
Designed by open format Ultriym, which uses 200 GB cassettes, and a data transfer rate of 20 Mbps. On the basis of these devices, digital storages were created - robotic libraries with a total capacity of 10 TB and a data transfer rate of up to 10 Mbps.
The Russian company Mobile TeleSystems (MTS) recently installed the Exabyte X200 tape library (one cabinet) that can store up to 30 TB of compressed data (this is the equivalent of 30 million volumes), for reserve copy and archiving billing (payment) records. The library consists of 200 cassettes, up to 150 GB per cassette, data transfer rate of 30 Mbps.
Compact optical discs
Read-only discs A CD-ROM with pre-recorded and unchanged information is one of the most reliable and common carriers of digital information. Such discs are especially useful for recording immutable information, such as archival or retrospective publications, collections of drawings, and similar data that may be required by a large number of users. It is useful to note the differences and similarities between the website and the optical disc. Although both types contain machine-readable information, the service disk is much closer to the print format. This is confirmed by library practice. The disk is physically owned, it can be cataloged and put on the shelf of the library. At the same time, there is a very important technological and logical unity: both technologies work in the mode of formation of standard information packets.
CD-ROM technology came about through collaboration between Sony (Japan) and Philips (Netherlands). In 1987, the International Organization for Standardization issued the international standard ISO 9660 “Information Processing - File and CD-ROM Volume Structure for the Exchange of Information (1988),” which currently corresponds to almost all market types of CD-ROMs.
Audio CD, or CD-ROM. - This is a disk with a diameter of 12 cm made of pure floor and carbonate plastic, coated with reflective metal (aluminum, gold) and a protective layer of transparent varnish. A focused laser beam reads the tiniest (0.5 micron) recesses along a spiral track with a total length of 4.5 km. The encoding density is very high: on the track of an audio CD, or CD-ROM. contains about 3 billion codes. On a standard CD, 74 minutes of sound or about 680 MB of information can be recorded. The disc does not have physically selected tracks and does not need formatting, and the recording goes along a kind of virtual spiral, making 20 thousand revolutions from the center out. Information is read from the disk when driving at a constant linear speed: the disk rotates more slowly (200 revolutions per minute) when the read head is on its outer part. Playback is carried out by devices built into the computer with the possibility of accelerated disk rotation (and data transfer) of multiplicity 8. 16, 32, 40 and higher.
Logical structure CD-ROM discs in ISO 9660 format have a four-level architecture: bit, byte, block, file. The physical structure is given below. This architecture allows the use of CD-ROMs with various operating systems as if it's just another one magnetic disk or file drive. The structure of the CD-ROM block is given in table. 31 (2352 bytes in each block).
The “Synchronization” field indicates the beginning of a block and sets the block counter to the desired position. The “Title” contains the address of the block and a description of the type of master data. The “Basic data” field contains a useful digital array, which can be text, graphics, sound recording, image. video. CD-ROM units include three levels of error detection and correction (EDC) and ECC (Error Correction Code), which are not used in audio discs.
Errors on the disk are most often associated with the appearance of scratches on its surface; Finding out their special routine is based on multiple cyclic verification of the sums of binary symbols. Error correction is carried out by a rather complicated program (Reed-Solomon cross-alternating encoding). These systems can reduce the expected level of errors on a CD-ROM to an extremely low value - 10 to minus 12 degrees, one error per trillion binary codes, or 1 error per 20 thousand disks!
Audio CDs do not need this precaution, and if an error occurs, the program will simply repeat the previous 1/75 second recording piece, which is completely inaccessible to the human ear.
To reproduce the information recorded on optical disks, at first, either free-standing devices or disk drives built into the computer were used. For professional purposes, storages for 50-100 disks with mechanical feed of disks to the reader (Juke Box) are used. Special multi-drive computer systems have also been created that can be read from several turning discs at the same time. However, the colossal memory capabilities of modern servers allow the transfer of information from CD-ROM or DVD and direct service from the hard drive; for example, the AXONIX server contains information written from 512 disks.
Nowadays, built-in devices for recording information on optical discs (write once or write once again) are very widespread as an addition to a regular hard drive of a computer: for example, a Mitsumi CR4808 TE drive with a capacity of 483 MB.
Further development of the technology of audio CDs went in two directions. The first is enhanced CDs (Super Audio Compact Disc, SACD) due to the very high sampling frequency (2822.4 kHz compared to 44.1 kHz), providing a new sound quality - surround sound. Initial developers went this way
Audio CDs - Sony and Philips.
In parallel, another direction is developing - high-density double-sided discs (they are called DVD - Digital Versatile Disk or Digital Video Disk; meaning the possibility of this drive record full movies) with 4.7 GB of memory on one side of the disc. Now, the leading companies in the world have agreed on a standard of a rewritable laser in the blue part of the spectrum of an Audio DVD disc with a capacity of 27 GB, with a guaranteed storage period of information of 100 years. In the same way as in CD systems, a family of rewritable discs has been created in DVDs that are promising for use in libraries and information centers, for example DVD-RW (1 thousand rewrites) and DVD-RAM (100 thousand rewrites). Magneto-optical disks with a diameter of 3.5 inches with a capacity of 2.3 GB and Fujitsu drives are also interesting. The service life of such a disk is more than 70 years, more than 10 million overwrites are allowed, access to data at a speed of 8 Mbps. The recommended price of the drive is $ 300, one drive is $ 18, that is, the unit cost is less than 1 cent per megabyte.
At the beginning of 2005, leading US firms stopped production of VHS VCRs, which are replaced by optical dVD discs 20 GB capacity, which so far represent two competing optical disc formats. One is the so-called negative HD-DVD format, dVD-R discs with the ability to record. Rewritable DVD-RW with a capacity of 4.6 GB, developed by Toshiba NEC, Sanyo and supported by Paramaunt Pictures, Warner Bros .. Universal Pictures. The competitor is the advanced “plus” Blue-Ray format with the ability to supplement DVD + R recordings and DVD + RW discs with the ability to adjust and edit recordings, respectively developed by Sony and supported by Hewlett Packard and Dell. The specific cost of storing data on this type of disk is 15-20 cents per gigabyte.
The dominant market role of standard, traditional CDs is seen in Table. 1.
Table 1
The market role of various types of audio and video discs (the number and volume of sales in the world in 2003) *
Task number 1
To study the technology of recording on CDs, CDs and DVDs, industrial replication of CDs and DVDs, the technology for recording BLU-RAY, equipment and software. To prepare a reporting document with illustrations of equipment and recording schemes.
Task number 2
Consider types of hard drives ( IDE / ATA, UDMA , Uide , AT-6, Fast ata , Ultra ATA , SATA, SCSI)their characteristics ( capacity (capacity) access time (access time), data rate (data transfer rate), packet rate / continuous data rate (burst / sustained), 5000/7200/10000 RPM)and hardware. Prepare a reporting document.
It is convenient to use external media to store and transfer information from one computer to another. Optical disks (CD, DVD, Blu-Ray), flash drives (flash drives) and most often act as storage media. external hard wheels. In this article we will analyze the types of external storage media and answer the question “What is the data stored on?”
Now optical discs are gradually fading into the background and this is understandable. Optical discs allow you to record a relatively small amount of information. Also, the convenience of using an optical disc leaves much to be desired, and besides, discs can be easily damaged and scratched, which leads to a loss of readability of the disc. However, for long-term storage of media information (films, music), optical discs are suitable like no other external media. All media centers and video players still play optical discs.
Flash drives
Flash drives or simply “flash drive” is now in greatest demand among users. Its small size and impressive memory capacity (up to 64GB or more) allow you to use it for various purposes. Most often, flash drives are connected to a computer or media center through uSB port. A distinctive feature of flash drives is the high speed of reading and writing. The flash drive has a plastic case, inside of which there is an electronic board with a memory chip.
USB sticks
A variety of flash drives include memory cards, which are a full-fledged USB flash drive with a card reader. Ease of use of such a tandem allows you to store significant amounts of information on various memory cards, which will occupy a minimum of space. In addition, you can always read the memory card of your smartphone, camera.
Flash drives are convenient to use in everyday life - transfer documents, save and copy various files, watch videos and listen to music.
external HDs
External hard drives are technically a hard drive housed in a compact case with a USB adapter and anti-vibration system. As you know, hard drives have impressive volumes disk spacethat coupled with mobility makes them very attractive. On your external hard drive, you can store all your video and audio collection. However, for optimal performance external hard drive requires increased power. One USB port is not able to provide full power. That's why external hard drives have dual uSB cable. The external hard drives are small in size, and can easily fit in a regular pocket.
HDD boxes
There are HDD boxes designed for use as a storage medium ordinary hard disk (HDD). Such boxes are a box with a USB controller, to which the simplest hard drives of a desktop computer are connected.
Thus, you can easily transfer information directly from the hard drive of your computer directly, without additional copying and pasting. This option will be much cheaper than buying an external hard drive, especially if you need to transfer almost the entire amount to another computer. hard section drive.
What is HDD, hard disk and hard drive - these words are different widespread terms of the same device that is part of the computer. Due to the need to store information on a computer, devices appeared, information storages as a hard disk and became an integral part of a personal computer.
Previously, on the first computers, information was stored on punched tapes - this is cardboard paper with punched holes; the next step in human development of the computer was magnetic recording, the principle of which is preserved in current hard drives. Unlike today's terabyte HDDs, the information to be stored on them totaled tens of kilobytes, which is an insignificant amount compared to today's information.
Why do I need a HDD and its functionality
HDD - this is a permanent storage device of a computer, that is, its main function is long-term storage data. HDD, unlike RAM, is not considered volatile memory, that is, after disconnecting power from the computer, and then, as a result, from hard drive, all information previously stored on this drive will be saved. It turns out that the hard disk serves as the best place on a computer to store personal information: files, photos, documents and videos will obviously be stored for a long time on it, and the stored information can be used in the future in your needs.
ATA / PATA (IDE) - this parallel interface is not only for connecting hard drives, but also devices for reading discs - optical drives. Ultra ATA is the most advanced representative of the standard and has a possible data usage rate of information up to 133 megabytes per second. The indicated method of data transfer is considered to be very outdated and is used today in outdated computers; on modern motherboards, the IDE connector can no longer be found.
SATA (Serial ATA) - It is a serial interface, which has become a good replacement for outdated PATA and, unlike it, it is possible to connect only one device, but on budget motherboards, there are several connectors for connection. The standard is divided into audits having different speeds data transfer / exchange:
- SATA has a data transfer rate of up to 150 Mb / s. (1.2 Gbit / s);
- SATA rev. 2.0 - in this revision, the data exchange rate in comparison with the first SATA interface increased 2 times to 300 MB / s (2.4 Gb / s);
- SATA rev. 3.0 - data exchange at the audit has become even higher up to 6 Gb / s (600 MB / s).
All the above SATA family connection interfaces are interchangeable, but by connecting, for example, a hard drive with sATA interface 2 to connector motherboard SATA data exchange with hard drive will be held based on the oldest revision, in this case SATA revision 1.0.
