Name «Winchester»

According to one version of the title of «hard disk» drive was through the company IBM, which in 1973 released a hard disk drive models 3340, for the first time united in one indivisible body of the plate and disk reading heads. In its development engineers used a short internal name «30-30», which meant two modules (the maximum configuration) to 30 MB each. Kenneth Hoton, project manager, to accord with the symbol of popular hunting guns «Winchester 30-30» invited to call this CD «disk».

In Europe and the United States called «hard disk» came into disuse in the 1990’s, the Russian language survived and received semiofficial status, but declined to computer slang words «screw» (most upotrebimy option), «Vinci» and «broom» .

Specifications
Disassembled hard drive Quantum fireball (model 2001)

Interface – a set of lines, the signals sent on these lines, the technical tools that support these lines, and rules (protocol) exchange. Normal production of hard disks can use the ATA (also known as IDE), SATA, SCSI, SAS, FireWire, USB, SDIO, and Fibre Channel.

Capacity – the amount of data that can be stored drive. The capacity of modern devices to 2000 GB (2 TB). In contrast, of the information system of prefixes that denote multiples of the value of 1024, manufacturers in the marking of containers of hard disks used values divisible by 1000. Thus, the capacity of the hard disk, marked as «200 GB», is 186.2 flexibility.

Physical size (form factor). Almost all modern (2001-2008 year) drives for PCs and servers have a width of 3.5 or 2.5 inches – the size standard for the fastenings are in desktop computers and laptops. Also, a proliferation of formats for 1.8 inch, 1.3 inch, 1 inch and 0.85 inches. Stopped production of drives in the form factor 8, and 5.25 inches.

Random-access time – the time for which the disk is guaranteed to perform your operation to read or write in any part of the magnetic disk. The range of this parameter is small – from 2.5 to 16 ms. Typically, the minimum time, have the server drives (for example, the Hitachi Ultrastar 15K147 – 3,7 ms), the largest of the topical – drives for portable devices (Seagate Momentus 5400.3 – 12,5).

The rotational speed of the spindle – the spindle number of revolutions per minute. From this setting rely heavily on access time and average speed data transmission. There are currently produced with the standard hard drive rotation speed: 4200, 5400 and 7200 (notebook), 5400, 7200 and 10 000 (personal computers), 10 000 and 15 000 rpm (high-performance servers and workstations).

Reliability – defined as the average time between failures developments (MTBF). Also, the vast majority of modern drives supports SMART.

Number of input / output operations per second – in modern disks is about 50 op. / S with random access to the drive and about 100 op. / sec, with sequential access.

Energy consumption – an important factor for mobile devices.

The level of noise – noise that produces a mechanical drive, with his work. It is stated in decibels. Quietest drives are devices with a noise level about 26 dB and below. Noise is noise from the spindle rotation (including air), and positioning noise.

Resistance shocks – a sharp rise in resistance to storage pressure or shock, measured in units of Non-switched and switched off.

Speed data transmission with sequential access:

* Inside the disc: from 44.2 to 74.5 MB / s;
* External disk Zone: from 60.0 to 111.4 MB / sec.

The volume of buffer – a buffer is called intermediate memory, designed to smooth out the differences of speed read / write and transfer to the interface. In the current (2008) HDD, it usually ranges from 8 to 32 MB.

Manufacturers

Most of all hard drive produced only a few companies: Seagate, Western Digital, Samsung, and also formerly owned by IBM unit to produce discs of Hitachi. Fujitsu continues to produce hard drives for notebooks and SCSI-drives, but left the mass market in 2001. Toshiba is a major producer of 2,5 – and 1,8-inch Railway Laptop. One of the leaders in the production of the disc is held by Maxtor. In 2006, the merger took place on Seagate and Maxtor. In mid-1990’s there was a company Conner, which bought a Seagate. In the first half of 1990, there was another company Micropolice, is very expensive premium-class drives. But with the release of the industry’s first hard drive to 7200 rpm it has been used substandard main shaft bearings supplied by Nidek, and Micropolice suffered a fatal loss of return, and was devastated at the root of the same bought Seagate.

The hard disk consists of germozony and electronics unit.

Germozona

Germozona includes a body of durable alloy actually discs (plates) with a magnetic coating, unit heads with the positioning device, electric spindle.

Block heads – a package of incentives from the springy steel (for the pair on each disc). In the end, they set out on the axis near the edge of the disc. At the other end (on CDs) are heads.

Discs (plates) are normally made of metal alloy. Although there were attempts to make them from plastic and even glass, but these plates were fragile and short-lived. The two plane plates, like the tape, covered with dust thinnest ferromagnetic – oxides of iron, manganese and other metals. The exact composition and technology application are kept secret. Most of the budget of devices contains 1 or 2 plates, but there are models with a large number of plates.

Discs fixed permanently on the spindle. During the spindle rotates at a speed of several thousand revolutions per minute (4200, 5400, 7200, 10 000, 15 000). At such a speed near the surface of the plate creates a powerful airflow that lifts the head and forces them to float above the surface of the plate. The form of head is calculated, so that when working to ensure the optimal distance from the plate. While the disks are not dispersed to the speed necessary to «take off» heads, a parking device holds the head in the parking area. This prevents damage to heads, and the working surface of plates.

Your head position is fixed a pair of strong, usually neodymium, permanent magnets and coils in the movable block heads.

Contrary to popular belief, inside germozony no vacuum. Some manufacturers make it a sealed (hence the name) and filled with purified and dried air or neutral gases, in particular, nitrogen, and to equalize the pressure set of thin metal or plastic membrane. (In this case, inside the hard drive provides a small pocket bag silica gel, which absorbs water vapor, remaining inside after it is sealed). Other manufacturers aligns the pressure through a small hole with a filter that can hold a very small (several micrometers) particles. However, in this case is leveled and humidity, but can also penetrate the harmful gases. Pressure needed to prevent deformation of the shell germozony at a barometric pressure and temperature, as well as in the warmup device during operation.

Dust caught in the assembly of germozone and trapped on the surface of the disk, rotating demolished for another filter – scrubber.

Block Electronics

In early hard drives control logic was introduced by MFM or RLL controller computer and the electronics board contains only analog modules are the processing and management spindle motor, positioner and switch heads. The increase in data rates has forced developers to reduce the limit to the length of the analog path, and the modern hard drives electronics unit usually includes: Managing a block, a permanent storage device (ROM), a buffer memory interface unit and digital signal processing.

Interface unit provides a pair of electronics hard drive with the rest of the system.

Block Management is a management system that takes electrical signals positioning of heads, and make managing the impact drive type «voice coil», switching the flow of information from different heads, the management of all other nodes (for example, control the speed of rotation of the spindle).

Block ROM stores control programs for motor control and digital signal processing, as well as proprietary information the hard drive.

The buffer memory overflow difference of velocities of the interface and the drive (using high-speed static RAM). Increase the size of the buffer memory, in some cases to increase the speed of the drive.

Digital signal processing which they carried out cleaning of the analog signal and its decoding (extraction of digital information). For the digital processing of various methods, such as method PRML (Partial Response Maximum Likelihood). A comparison of the received signal samples. This selected sample is most similar in shape and temporal characteristics of dekodiruemym signal.

At the final stage of assembling the device surface of the plates are formatted – they are the tracks and sectors. The specific method is determined by the manufacturer and / or standard, but as a minimum, each track is caused by the magnetic label indicating its beginning.

There are utilities that can test the physical disk sectors and the limited view and edit his or her data [6]. Specific capabilities of such tools are highly dependent on the disk model and technical information, known to the author by a family of models.

The geometry of the magnetic disk

With a view to addressing the space of the drive plates are divided into tracks – concentric annular region. Each track is divided into equal sections – sector. Addressing CHS assumes that all tracks have the same number of sectors.

Cylinder – a set of tracks, equidistant from the center, in all the working surfaces of the hard disk platter. Number of head sets used by the working surface (ie, a specific track within a cylinder), a number of sector – specific sector on the track.

To use addressing CHS, it is necessary to know the geometry of your disk: total # of cylinders, heads and sectors in it. Initially, the information required to set manually in the standard ATA-1 was introduced feature auto-geometry (the Identify Drive).

Features of the geometry of hard disks with integrated controllers

Zoning

On the plates of modern «HDD» tracks are grouped into several zones (English Zoned Recording). All tracks are the same zone have the same number of sectors. However, at the tracks outside of zones of sectors than in the inland tracks. This allows using long outer track to achieve a more uniform density, increasing the capacity of the plate with the same production technology.

Rezerv sectors

To increase the life of the drive at each track may be present additional back-up sectors. If in a sector or a Fatal error, this sector can be replaced Reserve (eng. remapping). The data stored in it, at the same time can be lost or restored with the help of ECC, a disk storage capacity will remain unchanged. There are two tables redirection: one is filled at the factory, another in the process of exploitation. The boundaries of zones, the number of sectors per track for each zone and the redirection table is stored in the memory sectors of the electronics unit.

Logical geometry

With the growing capacity of hard disks produced by their physical geometry ceases to fall within the limitations of software and hardware interfaces (see the barriers of hard drive). In addition, paths with different number of sectors are inconsistent with the manner of addressing CHS. As a result, disk controllers were not to report the real and fictitious, logical geometry, fit into the restrictions, but does not correspond to reality. Thus, the maximum number of sectors and heads for the majority of models are 63 and 255 (the maximum possible values in the functions of interruption BIOS int 13h), and the number of cylinders is selected to drive tanks. The very same physical disk geometry can not be obtained in the state mode of operation and other parts of the system is unknown.

Addressing these

The minimum reporting to the data on your hard disk is a sector. The sector is traditionally equal to 512 bytes. In 2006, IDEMA has announced the transition to a sector size of 4096 bytes, which is scheduled to be completed by 2010. In the final version of Windows Vista, released in 2007, has limited support for disks with the size of the sector.

There are 2 main ways of addressing the sectors on the disk: the cylinder-head-sector (CHS) and Linear Block Addressing (LBA).

CHS

In this mode sector is addressed by its physical position coordinates on the disc 3 – the number of cylinders, number of heads and number of sectors. In modern drives with embedded controllers, these coordinates are not relevant physical position on the disk sectors and are «logical coordinates» (see # Logical geometry, above).

LBA

This method only sets the number of sectors – with an absolute number on the disk. The standards require the ATA-1-one correspondence between the CHS and LBA:

LBA = [(Cylinder * no of heads + heads) * sectors / track] + (Sector-1)

Technologies recording data

The operating principle of the hard disk is like a work tape recorders. The working surface of the disc moves on the reader head (for example, in the form of coil inductance with the gap in the magnetic circuit). When alternating electrical current (in writing) to the head coil, the resulting alternating magnetic field from the head gap affects ferromagnetic surface of the disc and changes the direction of the magnetization vector of domains, depending on the size of the signal. If we read the movement of domains from the head gap leads to a change in magnetic flux in magnetic heads, which leads to a variable electrical signal in a coil due to the effect of electromagnetic induction.

Recently, readers use magnitorezistivny effect and is used in disk magnitorezistivnye head. In them, changing the magnetic field leads to a change in resistance, depending on changes in the magnetic field. Such a head to increase the likelihood of the reliability of reading of information (especially in high-density recording of information).

Parallel recording

At the moment it is still the most common technology of recording information on HD. Bits of information are recorded by using a small head, which passes over the surface of a rotating disk magnetize billions horizontal discrete areas – domains. Each of these areas is a logical zero or unity, depending on the magnetization.

Maximum achievable using this method, the recording density of about 23 Gbit / cm ². There is a gradual displacement of the technique using perpendicular recording.

The method of perpendicular recording

The method of perpendicular recording – a technology in which the bits of information stored in the vertical domains. This allows you to use a strong magnetic field and reduce the area of material required to record 1-bit. Density recording with modern designs – 15-23 Gb / cm ², in the future it is planned to bring the density up to 60-75 Gb / cm ².

Hard drives with perpendicular recording available on the market since 2005.

The method of thermal magnetic recording

Termoassistiruemaya magnetic recording

The method of thermal magnetic recording (eng. Heat-assisted magnetic recording, HAMR) at the moment the most promising of the existing, now it is actively being developed. When using this method uses a point-heating disk, which allows the head magnetize a very small area of its surface. Once the disk is cooled, the magnetization «lays down». In the market of railway of this type has not yet been presented (in 2009), there is only experimental models, but their density already exceeds 150 Gbit / cm ². Development HAMR-technology is already quite long, but experts still differ in estimates of maximum density. For example, a company called Hitachi limit 2,3-3,1 Tbit / cm ², and representatives of Seagate Technology, suggest that they can bring HAMR-density recording media up to 7.75 Tbit / cm ². Wide dissemination of this technology should be expected after 2010.