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2012/05/23 12:10:10

Hard drive (magnetic drive, winchester, HDD)

The hard drive (the magnetic drive, the winchester, HDD)  — the device for storage and data recording in computers using magnetic plates in the basis.


Principle of work

The principle of operation of the hard drive is rather simple. The typical winchester consists of several main nodes as that:

  • the body from shock-resistant alloy,
  • plates with a magnetic covering,
  • the block of heads with the device for positioning,
  • block of electronics and
  • electric drive.

Many users consider that hard drives are hermetic. However it not so  — inside is required to support constant pressure at fluctuations of temperatures. With respect thereto the hard drive is equipped with the filter which delays particles diameter to several micrometers.

The block of electronics contains own memory device and several subblocks which are responsible for digital processing of a signal, management and work with the interface. Operation of the most hard drive bears to structure of the tape recorder a strong resemblance. The working surface of a disk moves with a certain speed of rather read head. During the procedure of record or reading a head soar over a disk surface on the airbag. If the mote gets to a gap between a disk and a head, then heads can hit against a surface, spoil a disk and even to burn down.

The magnetic disk can be made not only of metal, but also of glass as it was in models from IBM. On a surface of a disk there is a magnetic layer which forms a basis for data recording. Bits of information register using a head which passing over a surface of the rotating disk magnetizes billions of horizontal discrete areas  — domains. Each of these areas is logical zero or unit, depending on magnetization.

Initially a pancake surface absolutely empty, i.e. magnetic domains are not focused in any way. For orientation of a magnetic head assembly special tags  — servo-tags are applied on a magnetic disk. It is performed by a "native" magnetic head assembly which is controlled in turn the external device. After a marking the hard drive itself is able to read information and to write on a surface. At large volumes of the winchester in it several magnetic disks which are fixed on the spindle engine are established, and form a shot glass of pancakes.


The interface  — generally defines the place or a method of connection/contact/communication. This term is used in the different fields of science and technology. Modern drives can use interfaces SATA, IDE USB, IEEE 1394  , etc.

The physical size (form factor)  — the set standard size of the hard drive. Drives for personal computers and servers have the size of 3.5 inches. Winchesters in a format 2.5 inches are more often used in notebooks. Other widespread formats  — 1.8 inches, 1.3 inches and 0.85 inches.

Spindle rotational speed  — amount of turnovers of a spindle in a minute. Time of access and data transfer rate substantially depend on this parameter. Now winchesters with the following standard rotational speeds are issued: 4200, 5400 and 7200 (notebooks), 7200 and 10,000 (personal computers), 10,000 and 15,000 RPM (servers and high-performance workstations).

Time of random access  is the Parameter of a peculiar assessment of speed of operation of the hard drive. In English the analog of random access time is used. The average time of access for modern models fluctuates from 3 to 15 ms. The value, the better is less. As a rule, server disks have the minimum time.

Market of HDD

Main article: Hard drives (world market)



For a Hard Disk Drive (HDD) phrase linguists use the name retronym – the term which is thought up by linguists for already new name of the existing phenomenon to distinguish it from something newer, in this case from floppy disks. And here strange situation: there are no floppy disks, there is no need to distinguish floppy disks from tough, and the retronym remained, but now it serves for difference of HDD from Solid State Drive/Disk (SSD) solid state drives which generally and disks that are not.

The present wave of public interest in SDD should not enter into doubt of relative future HDD, these disks lived and will live, constantly developing and being improved. In the nearest future there will be a disk with a capacity of 20 Tb, and the general release grows constantly for 1–3% a year.

In more detail about evolution of DWH read here.

Huge tape recorders

Success of disks looks as some incident. In the mechanical device which became an integral part of the electronic systems, time of movement of heads is measured absolutely by other values, than the speed of electronic processes. In the union between electronics and mechanics paid attention to lack of harmony long ago, still in the fifties when the first disks were created. But then to mechanics there was no alternative as semiconductor technologies took only the first steps, it was necessary to go consciously for mismatch for the sake of achievement of the goal, however it was more than successful. Direct access to big (to those measures) was the purpose to volumes this which remained it is impossible until data were read out in a flow either from a tape, or from punched cards. Data, read from the carrier, could be placed or in tiny RAM, or to do swapping and to pump up data from a drum. In some operating systems there were utilities for reading files from tapes, but it was awfully slow process.

At an early stage of development of computer systems standard hard drives were only pilot models. Computers resembled huge tape recorders. In principle record and reading information did not differ from an ordinary kassetnik at all  — data were had linearly. Those who also remember the PC on the basis of carriers with a magnetic film, know what it to wait for loading of the next level  — ordinary rewind of the cartridge on the right place.

The first personal computers used as the drive normal cassette audio the tape recorder. The disk drive for them was unattainable luxury. Those users at whom together with the PC the disk drive was delivered could already feel semblance of freedom of action. The first computers of IBM company were delivered with one or two disk drives.

Rabinov's disks

The idea of a disk as devices with moving on space heads lay on a surface and attempts to implement it were made by many companies. In the Computer museum in Mountain I Twist several options of disks are stored. Commercial success before others came to IBM capable to spend for development more than the others therefore in all chronicles of evolution of disks as starting point date 1956 and the drive on disks which was a part of the RAMAC IBM 305 computer (Random Access Method of Accounting and Control) in which name it is directly specified its possibility of random access, unique on that time, – Random Access Method is specified.

But IBM was not the first. Before all the working drive was made by the gifted inventor Yakov Rabinov (1910-1999) in 1951 who gave all life to work in National bureau of standards. He was born in Kharkiv, in the original its surname was Rabinovich, after the revolution in 1921 he with parents through China moved to the USA, and then worked nearly 70 years in research division of National bureau of standards. Rabinov did not become a scientist, but he was a genius of practical inventions, among them, for example, the advanced technology of stamping prolonging the term of life of coins, the invention brought to the State treasury many billion economy on release of a metal trifle. However, only one of its inventions – the device which was called Notched-Disk Magnetic Memory Device – did not bring it either money, or lifetime recognition. It consisted of ten 18 inch "pancakes", so in the subsequent began to call actually disks, with the cut segment that they could be changed for axes.

Experts from IBM studied Rabinov's invention and did not hide a priority. Having analyzed Rabinov's disk, in 1953 they issued the report of "The offer on random access to data files" (A Proposal for Rapid Random Access File) which became a RAMAC project basis.

In more detail about evolution of DWH read here.

1956: IBM RAMAC is a cabinet of 975 kg

The first drive of IBM on disks did not exist as a single product, it was a part of the RAMAC IBM 305 computer and consisted of fifty a 24-ta of the inch pancakes rotating with a speed of 2000 RPM, the general capacity was 3.75 MB that is equivalent to 64,000 punched cards.

The sizes of the winchester were simply huge. In practice it was  the cabinet weighing 975 kg which comprised 50  plates with a diameter about 60 cm everyone. Plates were mounted on a live spindle, and the mechanical bracket contained heads of a read and write. It moved up and down on a vertical rod, and time of transportation of a head to the necessary magnetic track was about one second. If to consider that now on accomplishment of this procedure milliseconds are required, then today such digit raises a smile.

The device weighing about a ton was not on sale, it could be taken in leasing only. In the subsequent the same strategy remained at release of models 650, 1401, 1410 and 7070 and only in 1962 there was a drive Model 1301 which was delivered separately from the computer. In it floating heads for the first time appeared, they were located on a comb on one head on each pancake. Capacity of Model 1301 was 28 MB.

The 1960th: Market development

Rabinov's invention was not protected by patent law in the USA therefore in disk business the set of the companies instantly rushed, at peak their total number reached 138, but in process of complication of production technologies the most part them left the market, and by 2015 remained Seagate, Toshiba and Western Digital, each of three about a third of the market belongs.

At first the Bryant Computer Products company which before others applied floating heads and zoning became one of the most successful (data writing it is proportional to length of the track changing on diameter). Bryant released the drive with the biggest pancakes with a diameter of 39 inches, them was 26, and the total capacitance was record too – 205 MB.

The next step in development of disk storage modules was taken by IBM in 1962 with release of the drive Model 1311, it differed from predecessors in emergence of the removable medium in which the pancakes reduced up to 14 inches, sbiratsya on a spindle in a packet. This step was revolutionary: first, a price compromise – on one expensive drive became possible to put cheap packets in an unlimited number, secondly, a limit for volume of the stored data was lifted and, in the third, security – packets was it is possible to contain out of the computer hall. Devices of this type became the standard de facto not only for meyfreym, but also for more numerous minicomputers. Production of packets with a capacity of 100 or 200 MB according to the standard of IBM joined a large number of the companies, there was a certain standard de facto, as a result of 14 inch disks more than 20 years up to mass distribution of disks winchesters held on in the market.

1973: Emergence of the term "winchester"

The hard drive received the name "winchester" in 1973 during creation of memory block of IBM 3340 which for the first time integrated in one one-piece body of a plate of a disk and read heads. The Kernet Horton project manager suggested to call so the device by analogy with a fowling piece of Winchester 30-30. The matter is that during operation over a disk engineers used working name 30-30 as the carrier consisted of two modules on 30 MB everyone.

The 1970th: Improvement of characteristics

In the seventies two directions in development of disks coexisted. One inherited the ideas which remained since IBM Model 1301, it assumed to build big, fast, but very expensive drives like IBM of 3380 Direct Access Storage Device which the first overcame a gigabyte boundary. Only the state organizations or the largest corporations could be consumers of such piece devices.

The second way – development of the idea of the removable packets differing from 14 inch in the fact that in a packet in addition to actually disks also yokes with drives are placed.

The drive of IBM 3340 Direct Access Storage Facility became an example of this direction, his code name at the time of design was Winchester, it for the first time appeared in 1973. This nickname remained for IBM 3340 for the reason that in it two packets on 30 MB, 30-30 were established, as in the known gun. It is curious that words the winchester and also the copier, as nominal namings as in Russian, in English are not used.

Transition to winchesters became possible at the expense of a preliminary marking of disks on which surface managing servodorozhka are applied. In the drawing (a) the scheme of work of the disk RAMAC, on (b) – a 14-inch disk is shown, in them expensive precision drives are installed. And on winchesters (c) and (d) the drive is significantly simpler, here it is only required to bring a yoke to the necessary track, the head "seizes it, between a servodorozhka and a head a feedback is established, and it will remain before the following movement of a yoke.

On it the background of disks comes to an end and begins absolutely another contemporary history, it is less evident, but is extremely interesting from the engineering point of view.

Times of unique disk devices remained in the past, first of all under the influence of mass production of the PC for which were required cheap, small by the size, but drives, big on capacity. This requirement could be satisfied, having arranged mass production of disks with a diameter of 5, 3.5 and 2.5 inches and having adopted standards of the SCSI and ATA interfaces. From these disks it was possible to collect reliable and high-performance arrays on RAID technology. Separate and more detailed consideration is deserved by file systems, technologies of virtualization and distributed systems of storage and, of course the solid state drives, modern interfaces and network technologies applied with DWH.

In more detail about evolution of DWH read here.

The 2000th: Perpendicular magnetic record

When HDD producers faced a capacity limit at the beginning of the 2000th, Toshiba and Seagate arranged arrangement of data bits on a disk plate. Change with longitudinal increased the capacity of HDD by the perpendicular magnetic record neither more nor less by 10 times.

2012: Density of placement of information on disks can double by 2016

The maximum density of placement of information on hard drives can double by 2016, according to another research IHS iSuppli published in 2012. Earlier the similar forecast was already made by the producer of hard drives Seagate company. According to analysts, it will expand possibilities of use of HDD in systems with large volumes of data, including audio and the visual systems.

A number of technologies on which vendors work now, in particular, technology of the warm magnetic record (heat-assisted magnetic recording, HAMR) which Seagate patented in 2006 will allow to increase density of hard drives. The company also stated that it will be able to release a 3.5-inch disk on 60 Tb by 2016. Disks of notebooks can already reach by the same time 10-20 Tb, said in the forecast of IHS iSuppli.

Analysts also note that recording density will grow to the maximum 1800 Gbit per square inch by 2016, for 2011 the similar indicator was 744 Gbit. According to IHS iSuppli, information recording density by a disk will increase by 2016 to 1800 Gbit per square inch from 744 Gbit in 2011. From 2011 to 2016 increase in recording density at HDD will be to increase on average by 19% a year.

For date of an exit of the research HDD with the maximum density it is released by Seagate in September, 2011: the disk size – 3.5 inches is located on it 4tb data. Density of a disk is 625 Gbit per square inch.

2013-2014: The imposed recording tracks and disks filled with helium

When the industry of HDD faced a capacity limit again in 2013, Seagate imposed recording tracks at each other as roofing gont, having increased the capacity per 25%; then in 2014, HGST provided the disks filled with helium, having increased the capacity per 50%.


Development of HAMR HDD

As in 2016 the prices of SSD continue to fall after implementation of technology of increase in density a flash of memory, such as 3D NAND, producers of hard drives plan own technology upgrades. Bright example: That it is more dense to HAMR HDD which uses the laser on a head of reading \record of the hard drive to locate smaller bits on the rotating disk in comparison with the traditional magnetic record.

Both work as Western Digital and Seagate on HAMR HDD.

Modern idea of disks

Disks evolved in several trunk directions:

The present wave of public interest in SDD should not enter into doubt of relative future HDD, these disks lived and will live, constantly developing and being improved. In the nearest future there will be a disk with a capacity of 20 Tb, and the general release grows constantly for 1–3% a year.

fall forward and tanks of disks; improvement of access to the data written to them; search of alternative solid-state technologies;

Development in the first direction led to emergence of such HDD which are capable to store terabyte volumes and to support high exchange rates.

On the second – to creation of the disks of equipment rooms and software tools supporting work: the file systems capable to support terabyte disks and abstraction from storage physics, including high-speed interfaces, RAIDs providing high reliability of storage, networks of storage of SAN and the network drives NAS.

On the third – to emergence quite recently the created solid-state devices of the corporate level (Solid State Device, SSD) in combination with the NVMe interface focused on these devices. Now the possibility of "smart storage", i.e. automatic redistribution of data storage, optimal on costs, between SSD, HDD and tapes depending on demand of data opened.

In more detail about evolution of DWH read here.