Hard Disk principles and knowledge

I. Main Components of the hard disk Disk: a hard disk is a magnetic particle attached to an aluminum alloy (new materials also use glass) disc on the surface. these magnetic particles are divided into several concentric circles called magnetic channels. On the magnetic channels of each concentric circle, there are several small magnets in any order. They represent the States of 0 and 1 respectively. When these small magnets are influenced by magnetic forces from the head, the direction of their arrangement changes accordingly. The magnetic control of the head is used to specify the direction of these small magnets so that each small magnet can be used to store information. Disk body: the disk body of a hard disk is composed of multiple disks. These disks overlap and are placed in a sealed box. they rotate at a high speed under the drive of the spindle motor, Head: the current head is mostly composed of multiple groups of heads. Generally divided into read group and write group. The Hard Disk Head is used to read or modify the magnetic material status on the disk. Generally, each magnetic surface has a head, starting from the top and starting from 0. When the head stops working, it is in contact with the disk, but is in a flying state during work. The head is started and stopped by means of a contact type in the landing area of the disc. The landing area does not store any data and the head is started and stopped in this area. Therefore, there is no problem of damage to any data. When reading data, the disk is rotated at a high speed. Due to the exquisite aerodynamic design of the head movement, the head is in a "flying state" at the height of 0.2 -- 0.3um from the data area of the disk ". It does not wear out due to contact with the disk surface, but can read data reliably. Motor: the motor in the hard disk has a spindle motor and a track motor. The motor in the hard disk is a brushless motor, and the mechanical wear is very small under the support of high-speed bearings, and can work continuously for a long time. High-speed rotation of the disk has a significant gyro effect, so the hard disk in the work should not be moved (or vibration), otherwise it will increase the bearing workload. The track finding motor of the hard disk head mostly adopts the sound ring rotation or linear motion stepping motor, which can precisely track and locate the track of the disc, so there should be no impact collision when the hard disk is working, be careful when moving. Ii. Working Principles of Hard Disks Currently, hard drives, whether ide or SCSI, use the "winchit" technology and all have the following features: 1. The head, disc and motion mechanism are sealed. 2. The flat and high-speed rotating disk flat and smooth surface. 3. The head moves radial along the disc. 4. The head starts or stops the Contact Type of the disk. However, the disk is not directly in contact with the disk. Therefore, there is no contact between the head and the data zone, so there is no data damage caused by the suspension of the head. 5. Spindle Motor Speed. The hard disk is rotated once it is started. The rotation of the spindle motor takes the sector of the data to be accessed to the bottom of the head, so the speed determines the final speed of the hard disk to a large extent, it is determined by the various technical parameters of the hard disk, and now the notebook is 5400 circles per minute or more. Home desktops are in 7200 circles per minute or more, and server categories are in around 10000 circles. No matter what operating system or software you use, they are being switched as long as one power is passed. Even after some software is used. The data read/write volume increases, but the maximum speed of the hard disk is fixed. 6. The track-finding motor supports reading data from the head. It is in a floating shape and moves back and forth between the left and right sides. It is very small and starts from the inmost (landing area) of the disc, slowly move to the outermost layer, and then slowly move back, one track and then to another track to find data. The shorter the tracing time, the faster the reading speed. However, this time is not determined by the system or software. It is also a fixed technical parameter of the hard disk and has an upper limit. Measured in milliseconds (MS. Performance of mainstream products between 5 ms and 10 ms is not significantly different. There will be no major jump (not a frog) that someone understands ). Therefore, its wear is almost negligible. No matter what software is used, it is impossible to break through its upper limit, so as to ensure that the hard disk works under the security state permitted by technology. There is no software damage to the hard disk. 8. cache size. Unit: MB. It is also a Fixed hard disk parameter. Its main function is to balance the internal and external transmission rates. In order to reduce the waiting time of the host, the hard disk first saves the read data to the buffer zone. After the buffer zone is filled up, it quickly sends a write to the host at the interface speed and writes the data to the hard disk. Currently, the cache of mainstream hard disks is between 2 mb--8 MB, and features such as pre-read, write cache, read cache, and segmented cache are available. 3. Heat Generation 1. It is generated by the rotation of the spindle motor and the track finding motor, and more importantly, the track finding motor. The hard disk temperature mainly comes from here. The noise is basically produced by the track finding motor. 2. friction between the high-speed rotating disc and the air. This is also the main factor. What about hard disk read/write? Unfortunately, its heat is completely negligible! 3. The read operation of the hard disk is the change of the magnetic field on the disk that affects the resistance value of the head. In this process, the disk won't heat up, but the head will generate a little heat because of the current change. But it is also small. 4. What about write operations? In turn, the current strength of the magnetic head is constantly changing, affecting the magnetic field on the disk. Because electromagnetic induction is used in this process, the heat of the magnetic head is high. But the disk itself will not heat, because the permanent magnet on the disk is cold, not because of magnetic field changes and fever. However, in general, the heat produced by the head is a little cool compared with the previous two. Heat can be transmitted by radiation, so will high heat damage the permanent magnet on the disk? In fact, the damage is very small. The temperature of the Permanent Magnet degaussing is much higher than the normal temperature of the hard disk. Of course, if your chassis has poor heat dissipation, it would be another thing. 4. Several statements questioning (1) "high temperature will damage the permanent magnet, resulting in Read and Write errors ". The situation should be: High Temperature affects the resistance sensitivity of the head, so it will generate a read/write error, and it has nothing to do with the permanent magnet. (2) "High Temperature produces thermal expansion, narrowing the distance between the disc and the head ". The problem should be: the flying state of the head is the aerodynamic principle. Under normal circumstances, it is always at a certain distance from the disk. If the temperature is so high that the head and disk are close to each other due to expansion, the chassis is melted before they are close. (3) "the use of some software causes repeated seek and reset operations on the head of the hard disk during reading and writing, thus damaging the hard disk ". Track seeking refers to moving the hard disk from the initial position to the specified track. The so-called reset action does not happen frequently. Because the physical location of the track is stored in the CMOs, the hard disk does not need to be moved back to the 0 track and then set off again. Unless you restart your computer, the reset will not happen again. (4) "The difference between a hard disk and a hard disk is too big ". SCSI, IDE, SATA, ATA, and CF cards refer to hard disk interface types. Although there are many hard disk interface types, they are widely used in personal computers, such as IDE, ATA, SATA interface hard drive. The SCSI interface is mainly used in the field of high-end servers/workstations. The CF card is used for ultra-small hard disks. Since various interface hard disks are designed in different fields, it is not suitable for simple comparison. The SATA interface has some advantages over the IDE interface hard disk. The structure of an IDE hard disk is similar to that of a SCSI hard disk. However, the interface bandwidth of the SCSI hard disk is larger than that of the IDE Hard Disk at the same time, and SCSI has something similar to the CPU to reduce the usage of the primary CPU. The speed of the SCSI hard disk is about 10000 laps per minute. That's all, so Seagate will use its SCSI hard disk technology on the IDE hard disk. (5) "Some download software (P2P technology) or playback software will damage the hard disk ". The read/write operations on a hard disk are measured in the sector of the cylindrical disk. The cylinder is the concentric track with the same radius of all the magnetic surfaces in the entire disk, and dividing each track into several zones is the so-called sector. The write operation of the hard disk is to fill one sector first, and then write the next sector of the same cylinder. Before the full write of one cylinder, the head will not be moved to another track. Therefore, the storage of files on hard disks is not stored in a continuous manner as most people think (from the perspective of users, but from the perspective of the underlying operating system, it is not stored continuously ). Therefore, when a download program has opened more threads, The seek of the head is generally not larger than playing a game while enjoying music. Of course, this is just a simple download or upload. But in this process, who can ensure that they will not start other software that requires hard disk reading and writing? Maybe many people like to play games or listen to music while downloading them? Not to mention that Windows itself needs to read and write virtual memory files frequently. Therefore, using express download, BT download, or any player will not increase the hard drive suffering or peacetime. 5. Hard Disk Protection (1) First, let's talk about why flash get is too multi-threaded, and why does BT read and write hard disks frequently. First, if there are more threads, the CPU usage will be high, and page feed will be performed frequently, resulting in frequent virtual memory read/write. What about BT? Download a file from several people at the same time, and several others are downloading your file at the same time, which is similar to flashget multi-thread. So the hard drive lights flash. However, you must understand that the hard disks that are widely used now have caches. data downloads are not written to the hard disk immediately, but stored in the cache first, and then write the data to the hard disk at a certain amount. This is the hard disk cache protection technology. No matter how it is set in the download program, it is written to the cache first. However, this process also requires CPU intervention. Therefore, the setting time is too short and the CPU usage is high. Therefore, the hard drive lights are still flashing because the virtual files are being read and written. (2) Hard Disk reading and writing are frequent, and the head arm moves frequently under the drive of the track motor. However, this loss is not significant for machinery. Unless your hard disk itself has mechanical faults, such as force arm deformation (the most common faults of water products ). The real wear loss lies in the head. The changing current will lead to its aging, but it should be within a reasonable range compared to its lifetime (continuous fault-free time. Unless the head hits the disk body due to vibration. (3) The most serious impact of high temperature is the mechanical circuit, especially the circuit board outside the hard disk. The Integrated Block above will accelerate aging at high temperature. Therefore, some hard disks seem to be useless due to heavy bad channels, and can be used again after a circuit board is changed. It seems that the bad channels are gone. That's the reason! (4) Hard Disks may affect the service life due to poor environment and improper maintenance, but this is definitely not a software error. Flashget, BT, and FTP are good. Although they read and write hard disks frequently, they do not hurt hard disks much as you normally play games and listen to music. To be more clear, the so-called hard drive wear loss of the software can be completely ignored. Don't worry about making guesses when you see a flash of hard drive lights. Look at the servers that provide Web Services and FTP services, and the computers of some management departments. Their hard disks are too large to read and write, so it is not common to play games. The hard disks of software can be compared. (5) the hard disk has a parameter called "continuous fault-free time" (note: "continuous "). It refers to the maximum time from the start of the hard disk to the occurrence of a fault, in the unit of hours, MTBF is short for English. Generally, the MTBF of a hard disk must be between and hours. For specific parameters, refer to the parameter description of the hard disk manufacturer. You can calculate the continuous fault-free time to see how many years it will take. Then, let's think about how long your hard disk has been working continuously for the longest time. I have a few friends who have been using the machine for one year. Except for several shutdown times in the middle for dozens of minutes to clean up the dust, I have never stopped it. In addition, there are three servers that use SCSI hard disks, which have not been stopped for two consecutive years. The hard disk's calorific value is not comparable to the ordinary IDE Hard Disk (10 thousand RPM hard disk ). Therefore, computers for general purposes do not have to trust the legends about hard drive damage. (6), it is best not to buy water or repair the hard disk. Water and cargo are mainly unsafe during transportation. Although it seems that there is no damage, it may cause damage to the mechanical body due to various factors during transportation. Not to mention repair. To be honest, those who complain that hard disks are easy to damage should check whether their hard disks are the same. (7) the working environment of the hard disk needs to be clean and tidy, especially when there are frequent power outages and a lot of dust. The chassis should be cleaned up every six months or so. (8), the hard drive machinery is most afraid of vibration. So the environment is better, especially the chassis should be solid, so as to avoid high resonance or resonance. Do not shake the computer desk. When you want to move the chassis, you must stop and power off. (9) The Hard Disk fragments should be sorted out frequently. There is a misunderstanding of most people. They all think that hard disk fragments will increase hard disk wear, but this is not the case. The increase in hard disk fragments only results in the hard disk reading and writing taking less time than the fragmentation. The hard disk loss can be ignored (here I will only say one fact, currently, the most commonly used operating systems for servers on the network are UNIX, but there is no disk fragment software in UNIX. Even Microsoft's NT4 does not exist ). However, as disk fragments increase and the head moves frequently, the read and write time increases, so the CPU page change will be frequent, this results in frequent reading and writing of virtual files (in fact, the correct statement here is the paging file), which increases the workload of Hard Disk Head seeking. This is the disadvantage of hard disk fragmentation. Another misunderstanding is that frequent disk fragmentation can damage the disk. The first thing to note is that no one will be able to sort out the disk in a day. It is usually done once every two or three months, or after a large number of installation and uninstallation operations, or after some intentional damage tests. The organization uses software to operate on files, and there is no damage to the hard disk, even if there is a little bit, as described above, it is completely negligible. Don't worry. (10) regularly check and correct errors on the hard disk. Regularly use the built-in chkdsk command in Windows to check and repair logical errors on the hard disk. Check the columns once in about half a year. If you find that the disk is a bit bad, you can check it. Although the Windows command tool is not powerful by a third party, it is safe and effective. (11) Avoid sudden power outages, cold start and other things that increase the CPU load during hard disk read/write (for example, enjoy music when playing a large game, or play a large 3D game when downloading at a higher speed). These damage to the hard disk is more serious than most people think. (12) when reinstalling the system, try to use the formatting program of the system installation disk to format the system zone. Partition formatting during system installation. Sometimes it is inexplicable to fix small problems on the disk. (13) once the hard disk is installed and used properly, try to avoid plugging the hard disk's data lines and power lines. The number of times that a hard disk connects to other devices is limited (the number of times is not verified or no authoritative reports are reported ). So try not to change it without plugging. Although SATA v2.0 and later versions support hot swapping, the motherboard also supports hot swapping. And even if both the hard disk and the motherboard support hot swapping, there is still a system and operation skill problem. In short, as long as the hard disk is used normally, the hard disk will not be so fast to talk to us about Byebye. Of course, if it is the quality of the hard disk itself, there is nothing to say.