Fundamentals of HDD

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HDD(hard disk or Fix disk) is a high-tech, high-precision industry, the Collector of semi-guide, laser light, precision machinery, advanced physics and other technologies. At present, the PC many weeks products in many countries can be made, only the CPU and hard disk only the United States, Japan and the ability to make, can see the difficulty of making. Because of the high technology involved in the hard drive, the American factory is generally not easy to access key technologies because of the strict control of the HDD technology.
The hard drive is the use of the 2-bit magnetic storage principle is to use it to control the power of the Reuters Hard drive Reader (Read/write Head), to change the surface of the magnetic chip of the micro-core of the positive polarity (﹢﹣) to be stored, so the few pieces of the magnetic film is important. And the magnetic chip is storing more information, it is necessary to make the magnetic core of the smaller (similar to the photographic particles of the camera film), and then coating (splash plated) to the surface of the magnetic sheet, the density is very high, and the hard disk read to be able to move in the magnetic surface of the high-speed back to read the information, you need to float on the surface of the magnetic sheet But too high to read the message will be too weak, can not reach the high capacity requirements, so it is possible to low pressure, its flight height (Flying height) about 0.5 UIn (can be likened to a large 747-passenger aircraft its flight height must be kept in 1 inch and not falling destroyed) so the surface of the magnetic sheet should be smooth, any differences , dust will cause the hard disk to read and write the damage magnetic surface (limited to 1 of the diameter of the hair) and cause permanent damage to the hard disk. As a result, the installation and repair of the hard drive will need to be done within the class 100 clean rooms (dust room), which is also the same as for information rescue.
Hard disk parts are roughly divided into pieces (Media), reading heads (Read write Head), spindle motor & Voice Coil motor, base (base), and circuit board (PCBA).
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With 3.5 "media, the 25mm, it is necessary to deduct the most outside and the most inner circle does not store the data part, actually only 20mm. Magnetic sheet is stored in 2 magnetic, the most magnetic powder, a magnetic powder only with or without electricity, "+" or "–"
A magnetic powder =1bit650) this.width=650; "title=" 63632225 "style=" border-top:0px solid;border-right:0px solid;border-bottom:0 PX solid;float:right;border-left:0px solid;line-height:20px; "alt=" 63632225 "src=" http://www.linwei.com.tw/upload/ Article_b/8406f440ee28fda1a98d6816f50b5c88.jpg "/>8bit=1byte
1mb=1024 x 1024=1,048,576byte
1gb=1,048,576 x 1,024=1,073,741,824byte100gb=107,374,182,400byte x 8Bit =858,993,459,200 Bit (magnetic particle)
(1 bit records 0 or 1,8bit can only record a single character such as a, B or C ....) In fact, it's not a bit, it's easy to understand, so it's described as bit. )

The density is high, so media is not contaminated, and the whole process needs to be in the clean room of class 100 cleanliness, which is why the hard drive needs to be disassembled in the cleaning room. When media is out of the factory, it is completely blank and no information is available, and it is required to be encoded by Servo track Write when it is installed by the respective hard drives.


650) this.width=650; "title=" a58547458a "style=" border-top:0px solid;border-right:0px solid;border-bottom:0px solid; float:left;border-left:0px solid; "alt=" a58547458a "src=" http://www.linwei.com.tw/upload/article_b/ 6dc57734c8400786d87abd81f448d3d6.jpg "/> Head is fixed on the same group arm by the upper and lower multiple pieces of reading, and moving back is the whole group of arm move together, generally read the principle is, for example: When 10MB data comes in, the 1th Head writes 4096 Byte First, the 2nd Head write 4096 Byte, according to this kind of push, vertical reading, so 1 files are divided into many segments exist on each magnetic surface, reading is also the same, so many magnetic head at the same time to read and write can reach the high-speed requirements, but now there are more advanced technology now. Arm because of the need to move back to the high-speed, non-chattering, and refined to the location of the site, the head verticality can not be a misunderstanding (limited to the 0.001﹪ width of the hair) so head, media are not relaxed or declination, or no legal track. At present, science and technology can not be wrong head or media to the original site, because the need to look at the X, Y Point and head of the vertical point, but also to take care of the diameter and the diameter of the tolerance, which is the hard drive afraid of collision reasons, it is not possible to switch head.

650) this.width=650; "title=" 32658555 "style=" border-top:0px solid;border-right:0px solid;border-bottom:0px solid; float:right;border-left:0px solid;line-height:20px; "alt=" 32658555 "src=" Http://www.linwei.com.tw/upload/article_ B/29140e12b64988b92f15cee9d0c18e85.jpg "/>Spindle MotorIt is mounted with 1 media at a speed of 7,200 or RPM, to keep its balance non-chattering, so bearing (beads,liquid) Quality requires severe kan, it is necessary to endure the continuous rotation of H x 365 days without abrasion, not producing high temperature noise.

When the hard drive is assembled, the spindle motor, media, Voice Coil motor, and head are fixed in sequence, testing the fly height value of each head in its media, whether it is qualified (approximately 0.5 UIn).
Because the head is used to float in the media without touching the principle of the movement can be at high speed to move back, but too high to read the message is too weak, too low to grind to the media surface, so the media surface should be smooth, any differences, Dust will cause the head to damage the magnetic surface and result in permanent data damage. Like the car in the high-speed tires to hit the big stone, the result is serious. As a result, the installation of the hard drive must be done in a high cleanliness and dust room. This installation requires the use of a laser detector, which cannot be used manually.


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100gb=107,374,182,400 byte/512byte=209,715,200 Sector.
Because too fine, Servo write is laser control, no misunderstanding. Because media is circular, the diameter is smaller, so the number of sector is less than the diameter, this is called the Zone Bit recording code, this is the most difficult technology.
Embedded Servo completed, this time the hard disk is ready to use, connected to the computer Power on, the Head can be normal orbit, the BIOS can Detect its specifications, the Sector value. At the end of the BIOS, the Controller is handed to the operating system, and the Data can be stored formally by the Create New Partition and Format.

the above basic principles, readers should be aware of a few questions to note:

1. Media is non-polluting, so it needs to be disassembled in class 100 clean with a high cleanliness.

2. Head, media two lip teeth dependent, when the initial fixed, that is, with Servo track writer will be the media for the vertical embedded Servo, there is no misunderstanding, as long as a slight collision, head can not be legal track, Therefore, it is not possible to remove or install head or media into another hard disk.

3. Media is a 2-bit magnetic medium, just like tape magnetic particles only a polar existence, so as long as the Head of the electricity can change its original value, so a damaged hard drive as long as the slightest careless, it is easy to be written into and destroy the original Data.

Fundamentals of HDD