Most hard disks are fixed and arePermanentThe ground seal is fixed atHard driveMedium.EarlyHard disk storagemediumIt is replaceable, but today's typical hard disk is a fixed storage medium, sealed in the hard disk (except for a filter hole, which is used for balancingair pressure）。With the developmentmobile hard disk driveIt also appeared, and became more and more popular, with more and more types.majoritymicrocomputerThe hard disk installed on the is called "Winchester hard disk" or "Winchester disk" for short because it adopts Winchester technology.
Ascomputer systemData forstorage, capacity is the most important parameter of hard disk.
The capacity of the hard diskMegabyteMegabyte（MB）, Gigabyte（GB）Terabyte（TB）Is the unit, 1GB=1024MB, 1TB=1024GB.But the hard disk manufacturerHard disk capacityUsually, 1GB=1000MB, so weBIOSThe capacity seen in or when formatting the hard disk is higher than that of the manufacturerNominal valueSmall.
The capacity index of hard disk also includesSingle disc capacity。The so-called single disk capacity refers to a single hard diskDiscThe larger the capacity of a single disk,Unit costThe lower,average access timeThe shorter it is.For users, the capacity of the hard disk is just like the memory, which will never be too small.Windows operating systemIn addition to easier operation, it also bringsfile sizeWith the increasing number, someapplication programIt is easy to eat up hundreds of megabytes of hard disk space, and there is a growing trend.Therefore, it is wise to purchase hard disks in advance.In the first two years, the mainstream hard disks are 320G and 500G, and the large capacity hard disks above 750G have also begun to be popular. In 2007, 1TB large capacity hard disks began to appear.
2. Speed
Computer hard disk
The rotational speed (Rotating Speed or Spindle Speed) is the rotational speed of the motor spindle in the hard disk, which is the maximum number of revolutions that the hard disk can complete in one minute.Rotating speed is one of the important parameters to mark the level of hard disk, which determines the internal quality of hard diskTransmission rateOne of the key factors directly affects the speed of hard disk to a large extent.The faster the speed of the hard diskFind FilesThe faster the speed oftransmission speed It has also been improved.Hard disk speedExpressed in revolutions per minute,Unit representationbyRPM, RPM is the abbreviation of Revolution Per minute, which is revolutions per minute.The higher the RPM value, the faster the internal transmission rate, the shorter the access time, and the better the overall performance of the hard disk.
The spindle motor of the hard disk drives the disc to rotate at high speed, producingbuoyancysendheadFloating above the disc.To bring the sector of data to be accessed below the head, the faster the speed iswaiting timeThe shorter it is.Therefore, the rotational speed largely determines the reading speed of the hard disk.
The rotational speed of ordinary domestic hard disks generally includes 5400rpm and 7200rpm. High rotational speed hard disks are the first choice for desktop users;For notebook users, it is mainly 4200rpm and 5400rpm, although some companies have released 7200rpmLaptop hard drive, but it is still rare in the market;Server users have the highest requirements for hard disk performance, and the SCSI used in the serverHard disk speedBasically, 10000rpm or even 15000rpm is used, and the performance is much better than that of household products.Higher rotational speed can shorten theAverage seek timeAnd the actual reading and writing time, but with the continuous increase of the hard disk speed, the temperature increases, the motor spindle wear increasesWorking noiseIncrease, etcnegative effect。The speed of notebook hard disk is lower than that of desktop hard disk, which is affected by this factor to some extent.The internal space of the notebook is small, and the size of the notebook hard disk (2.5 inches) is also designed to be smaller than the desktop hard disk (3.5 inchesThermal performancePut forward higher requirements;noiseAs it grows larger, necessary noise reduction measures must be taken, which put forward more requirements for notebook hard disk manufacturing technology.At the same time, the speed increases while others remain unchanged, which means that the power consumption of the motor will increase, the more electricity consumed per unit time, and theworking hoursShorten, so the portability of the notebook will be affected.Therefore, the notebook hard disk generally adopts the 4200rpm hard disk with relatively low rotational speed.
3. Access time
average access time(Average Access Time) means that the head reaches the target from the starting positionTrackPosition, and find the data to be read or written from the target tracka sectorTime required.
The average access time reflects the reading and writing speed of the hard disk, which includesSeek timeAnd waiting time, i.e. average access time=Average seek time+Average waiting time。
Average seek time of hard disk（Average Seek Time）It refers to the time required for the head of the hard disk to move to the specified track on the disk surface.Of course, the smaller the time, the better. The average seek time of a hard disk is usually between 8ms and 12ms, while that of a SCSI hard disk should be less than or equal to 8ms.
The waiting time of hard disk, also called latency（Latency）, which means that the head is already in theTrack, waiting for thea sectorTime to rotate below the head.Average waiting timeIt is half of the time required for the disc to rotate for one cycle, generally less than 4ms.
Internal Transfer Rate is also calledContinuous transmission rate(Sustained Transfer Rate), which reflects the hard diskbufferPerformance when not in use.The internal transfer rate mainly depends on the rotation speed of the hard disk.
Fast ATAThe maximum external transmission rate of the interface hard disk is 16.6MB/s, while that of the Ultra ATA interface hard disk is 33.3MB/s.
useSATA（Serial ATA）The hard disk of the port is also calledSerial hard disk, is the trend of PC hard disk in the future.In 2001, Intel, APT, DellIBM、Seagate、MaxtorThe Serial ATA Committee composed of these major manufacturers formally established the Serial ATA 1.0 specification.In 2002, althoughsata The related equipment of has not been officially launched, but the Serial ATA Committee has established the Serial ATA 2.0 specification first.Serial ATA adoptsSerial connection mode, Serial ATA bus uses embeddedclock signal, has a stronger error correction capability. Compared with the past, its biggest difference is that it can check transmission instructions (not only data), and if errors are found, it will automatically correct, which is greatly improveddata transmissionReliability.The serial interface also has simple structure and supportsHot plugAdvantages of.
5. Cache
Cache memory ishard disk controllerOne piece onMemory chip, with extremely fastAccess speed, which is between the internal storage of the hard disk and the external interfaceBuffer。Due to the internalData transmission speedDifferent from the transmission speed of the external interface, the cache plays a buffer role in it.The size and speed of the cache is an important factor directly related to the transmission speed of the hard disk, which can greatly improve the overall performance of the hard disk.When the hard disk accesses fragmentary data, it needs to constantly exchange data between the hard disk and the memory. With a large cache, the fragmentary data can be temporarily stored in the cache, reducing the load of external systems, and improving the data transmission speed
classification
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1. Memory communication
It is divided into XT type (i.eDMA mode）And AT type (i.e. interruptDrive mode）Two.
The disc diameter and capacity are 5.25 inches, 3.5 inches, 2.5 inches, 1.8 inches and 1.3 inches, and the smallest is the size of the nail cover.
fromOverall dimensionLook, there are full height, half height and thin type.
structure
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Hard disk is the most importantstorageone of.Most of the software that your computer needs to run properly is stored on your hard disk.becauseHard disk storageIt has a large capacity, which is different from memory and CD.The hard disk is based on the hard rotating disc used in the computerstorage device。It is stored and retrieved on a flat magnetic surfacedigital data。
head
Computer hard disk
The magnetic head is the most expensive component in the hard disk, and it is also the most important and critical link in the hard disk technology.The traditional magnetic head is an electromagnetic induction head that integrates reading and writing. However, the reading and writing of hard disk are two different operations. Therefore, the design of this two in one magnetic head must take into account both the reading and writing characteristics, which results in the limitation of hard disk design.MR magnetic heads, namelyreluctanceThe magnetic head adopts a separate head structure: the traditional magnetic induction head is still used as the writing head (the MR head cannot write), and the new MR head is used as the reading head, namely the so-called induction write and reluctance read.In this way, the two can be optimized according to their different characteristics during design to obtain the best read/write performance.In addition, the MR head senses the signal amplitude through the change of resistance rather than the change of current, so it is quite sensitive to the signal changeaccuracyIt is also improved accordingly.And because the signal amplitude read isTrackThe width is irrelevant, so the magnetic track can be made very narrow, which improves the disk density to 200MB/in2, while the traditional head can only reach 20MB/in2, which is the main reason why MR head is widely used.MR head has been widely usedMultilayer structureandMagnetoresistive effectMade of better materialsGMRGiant Magnetoresistive heads are also gradually popularized.
Track
When the disk rotates, if the head is kept in a position, each head will draw a circular track on the disk surface, which is called a track.These tracks are invisible to the naked eye, because they are only some magnetized areas magnetized in a special way on the disk surface, and the information on the disk is stored along these tracks.adjacentTrackThey are not close to each other, because the magnets will affect each other when the magnetizing units are too close, which also makes it difficult to read and write the magnetic head.One 1.44MB3.5 inch floppy disk, 80 tracks on one sideTrack densityIs much greater than this value, and there are usually thousands of tracks on one side.
The magnetic medium used for recording is coated on the surface of the disk, which shows magnetic particles under the microscope.The polarity of tiny magnetic particles can be quickly changed by the magnetic head, and can be stably maintained after the change. The system passesMagnetic fluxAnd the change of magnetoresistanceBinary0 or 1 in.It is precisely because all operations are carried out under microscopic conditions, so if the hard disk is subject to external force oscillation while running at high speed, it may be irretrievable because the head hits the disk surfaceData loss。In addition, the magnetic particleUniaxialHeterotropismAnd magnetic particles with obvious volumethermal stabilityThe thermal stability determines the stability of the magnetic particle state, that is, the correctness and stability of the stored data.However, the uniaxial anisotropy and volume of magnetic particles cannot be improved blindly, because they are limited by the write in field and media that the magnetic head can provideSignal-to-noise ratioLimitations of.
a sector
Every on diskTrackDivided into several equal partsArc segmentThese arc segments are the disk'sa sectorEach sector can store 512 bytes of information,disc driveWhen reading and writing data to the disk, the unit is sector.1.44MB3.5 inchfloppy disk, each track is divided into 18 sectors.
A hard disk is usually composed of a group of overlapping disks. Each disk surface is divided into an equal number of tracks and numbered from the "0" on the outer edge. Tracks with the same number form a cylinder, which is called the disk cylinder.Of disksCylinders With theTrackThe numbers are equal.Since each disk has its own head, the number of disks is equal to the totalHeads 。So called hard diskCHS, namely Cylinder, Head and Sector. As long as the number of CHS of the hard disk is known, the capacity of the hard disk can be determined. The capacity of the hard disk=number of cylinders × number of heads × number of sectors × 512B.[1]
usage method
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When the hard disk is working, do not forcibly turn off the power.Turning off the power when the hard disk is working will cause the hard disk toPhysical damage, and data will be lost.In addition, there are high-speed components in the hard disk. If the hard disk is forced to shut down, the high-speed disk will suddenly stop. If the hard disk is turned on immediately after the shutdown, it is more likely to cause damage to the hard disk.Therefore, do not turn on the computer again immediately after shutdown.Turn it back on at least half a minute later.
When the hard disk is working, try to avoid its vibration, because the magnetic head is very close to the magnetic sheet. If the hard disk is subjected to severe vibration, the magnetic head will hit the magnetic sheet, which may scratch the magnetic sheet, or cause complete damage to the magnetic head, making the whole hard disk unusable.
In the process of using the hard disk, many users will oftenSpace management”Compression is performed.Use this program to compress your hard disk.This will causeCompress volumeThe file keeps growing.The team will also slow down and the number of reads and writes will increase, which will affect the heat output and stability of the hard disk.Therefore, the service life will be reduced.Therefore, if the hard disk is enough, there is no need to use this program.
Proper maintenance
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Hard disk is very afraid of dust.If the dust is sucked onto the circuit board, it will lead to unstable operation of the hard disk or damage of internal parts.Functions of hard diskworking condition It has a lot to do with life and temperature. Too high or too low temperature will causecrystal oscillator The main frequency of the clock changes, which will causeCircuit elementFailure. If the temperature is too low, the moisture in the air will condense on the element, resulting in a short circuit.
Secondly, clean the hard disk regularly.This will speed up the hard drive.If theJunk FilesIf there are too many, the speed will slow down and may be damagedTrack。However, do not clean the hard disk every three days. This will also reduce the life of the hard disk.
Finally, it is anti poison.VirusesThe files stored on the hard disk are one of the biggest threats.So we found that the virus should be removed in a timely manner, and try not to format the hard disk.
matters needing attention
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1. Do not shut down suddenly when working
Computer hard disk
When the hard disk starts to work, it is generally in high-speed rotation. If we suddenly turn off the power in the middle, it may cause violent friction between the head and the disk and damage the hard disk. Therefore, we should avoid sudden shutdown.Be sure to pay attention to the hard disk on the panel when powering offindicator lightWhether it is still blinking, you can turn off the power switch of the computer only after its indicator stops blinking and the hard disk reading and writing is completed.
2. Prevent dust from entering
Dust can cause great damage to the hard disk. This is because in a dusty environment, the hard disk can easily attract dust particles in the air, which can accumulate on the internal circuit components of the hard disk for a long time and affectElectronic componentsThe temperature of circuit components will rise due to the heat dissipation of, resulting in leakage or burning of components.
In addition, dust may also absorb moisture, corrode the electronic circuit inside the hard disk, and cause some inexplicable problems. Therefore, although the dust volume is small, its harm to the hard disk cannot be underestimated.Therefore, environmental sanitation must be maintained to reduce the humidity andDust content。Remember: General computer users cannot remove the hard disk cover by themselves, otherwise the dust in the air will enter the hard disk and scratch the disk or the head when the head is reading or writing.
3. To prevent the temperature from being too high or too low
Temperature also has an impact on the life of the hard disk.The hard disk will generate some heat when it works, and there is a heat dissipation problem in use.The temperature should be 20~25 ℃, too high or too low will makecrystal oscillator The clock main frequency of has changed.Temperature will also cause failure of hard disk circuit components, and magnetic media will also cause recording errors due to thermal expansion effect.If the temperature is too low, the moisture in the air will be condensed on the integrated circuit components, causing a short circuit;When the humidity is too high, the surface of electronic components may absorb a layer of water film, oxidize and corrode the electronic circuit, so thatpoor contact, or even short circuit, the magnetic force of the magnetic medium will change, resulting in data reading and writing errors;Too low humidity, easy to accumulate a large amount ofelectrostatic charge, thus burning outcmos circuits , absorb dust and damage the head and scratch the disk.In addition, try not to make the hard disk close to a strong magnetic field, such as speakers, speakers, motors, radio stations, mobile phones, etc., to avoid damage to the data recorded by the hard disk due to magnetization.[2]
Considering the cooling effect, many people have installed a hard disk cooling fan for their computer hard disk. But some low-end fans have obvious vibration, which can transmit the vibration to the hard disk. In the long run, it will have an impact on the life of the hard disk.
2、 Optical drive
The reading speed of mainstream optical disk drive has reached more than 50 times. When the optical disk rotates at high speed in the optical disk drive, the vibration from the optical disk drive itself will drive the resonance of the chassis, thus affecting the work of the hard disk.And this high-speed rotationCalorific valueThere are many, too. The optical drive is so close to the hard disk, and the heat released from the optical drive will definitely make the temperature of the hard disk rise.
3、 Dust
The damage of dust to the hard disk is obvious. The dust deposited on the circuit board of the hard disk will seriously affect the heat emission of the chip on the circuit board, causing the temperature of the components on the circuit board to rise, thus causing the chip to overheat and burn.In addition, if dust absorbs moisture, it is easy to causeShort circuitOf.
4、 Static electricity
In the process of computer maintenance, many people use their hands to hold the hard disk, but in dry weather, people may accumulate tens of thousands of volts of static electricity on their hands, which may break down the chip on the circuit board, causing the hard disk to malfunction.
If the computer hard disk appearsBad trackMany netizens take low-level formatting measures. In factLow levelThe damage to the hard disk is very serious. It may cause the spread of bad tracks on the disk, or even lead to the loss of hard disk parameters, resulting in the hard disk can not be used.
6、 Power supply
A low-quality computer power supply will make the hard diskvoltage fluctuationEspecially when the hard disk is reading and writing, if there is a problem with the power supply of the computer, one hard disk can be scrapped almost instantly.
7、 Magnetic field
Because hard disk is a kind of dependenceMagnetic mediumIf the equipment used to record data is affected by the external environmentMagnetic field interference, which may lead to the loss of disk data, so you should try to stay away from the magnetic field environment.[3]
