The principle of hard disk reading and writing, how the hard disk reads and writes data

How hard drives work.

Today's hard drives, whether IDE or SCSI, use Winchester's technology, which has the following characteristics:

1。Magnetic head, disc and kinematic mechanism sealed.

2。The surface of the plated disc plate, which is fixed and rotated at high speed, is flat and smooth.

3。The head moves radially along the platter.

4。The magnetic head starts and stops in contact with the platter, but it is in flight and does not have direct contact with the platter when working.

Platter: A hard disk platter is a magnetic particle attached to the surface of an aluminum alloy (glass is also used for new materials). These magnetic powders.

It is divided into a number of concentric circles called tracks, and on the tracks of each concentric circle there seem to be an infinite number of small ones in any arrangement.

magnets, which represent the states of 0 and 1, respectively. When these small magnets are subjected to the magnetic force from the head, they are aligned.

The direction will change accordingly. Use the magnetic force of the head to control the direction of some small magnets so that each small magnet can be used.

Storing Information. Disk: The disk body of a hard drive is made up of multiple platters that are stacked on top of each other in a sealed box, and they are in the main case.

Driven by the shaft motor, it rotates at a very high speed, and its speed per minute reaches 3600, 4500, 5400, 7200 or even more.

Head: The head of the hard disk is used to read or modify the state of the magnetic material on the platter, generally speaking, each magnetic surface will.

There is a head, starting at the top, numbered from 0. When the head stops working, it is in contact with the disk, however.

Fly while working. The magnetic head adopts a contact start-stop method in the landing area of the platter, and the landing area does not store any number.

According to the report, the head starts and stops in this area, and there is no problem of damaging any data. When reading the data, the platter rotates at high speed, due to.

The head movement is aerodynamically designed so that the head is micron tall from the data area of the disk.

degrees of "flight status". It does not cause wear and tear in contact with the disc surface, and can read the data in the first place.

Motor: The motors in the hard disk are all brushless motors, which have little mechanical wear and tear under the support of high-speed bearings, and can work continuously for a long time.

Make. The high-speed rotation of the disk produces an obvious gyroscopic effect, so the hard disk at work should not be moved, otherwise the axis will be weighted.

workload. The seek feeding motor of the hard disk head mostly adopts voice coil rotation or linear motion stepper motor, which is feeding.

Under the adjustment of service tracking, the track of the platter is accurately tracked, so there should be no impact collision when the hard disk is working, and it should be small when moving.

The heart is relaxed.

1. Mechanical hard disk is a traditional ordinary hard disk, which is mainly composed of: platter, head, platter shaft and control motor, head controller, data conversion, interface, cache and other parts.

2. The platter is the medium that carries data storage in the hard disk. Hard disk platters are based on strong and durable materials, and the magnetic powder is attached to the surface of aluminum alloy (glass is also used in new materials), and the surface is processed quite smoothly. These magnetic particles are divided into concentric circles called tracks, and on each concentric track there are as if there are countless small magnets in any arrangement, which represent states of 0 and 1, respectively.

When these small magnets are subjected to a magnetic force from the head, the direction of their alignment changes.

3. The hard disk head is the key component of the hard disk to read data, it is 3nm away from the disk, and its main function is to convert the magnetic information stored on the hard disk platter into electrical signals to transmit outward, or to change the magnetic material of the disk through the electromagnet above it to write data. When the head needs to read or write the contents of different sectors of different tracks, it needs to constantly switch positions, and there will be a delay.

4. The main body of the SSD is actually a PCB board, and the most basic accessories on this PCB board are the control chip, the cache chip (some low-end hard disks do not have a cache chip) and the flash memory chip used to store data.

5. The main control chip is the brain of the solid state drive, and its role is to reasonably allocate the load of data on each flash memory chip, and the second is to undertake the entire data transfer and connect the flash memory chip and the external SATA interface. There is a big difference in the ability between different main controllers, and there will be great differences in data processing capabilities, algorithms, and read and write control of flash memory chips, which will directly lead to a gap of dozens of times in the performance of SSD products.

6. Solid-state drives, like traditional hard disks, require high-speed cache chips to assist the main control chip for data processing. It should be noted here that there are some cheap SSD solutions that save costs by omitting this cache chip, which will have a certain impact on the performance when used.

The USB flash drive uses flash memory as the storage unit, which is a kind of rewritable memory, and its carrier is a semiconductor chip. Ordinary memory is a type of RAM that loses all data when the power is off, while flash memory has to be powered up to change the data, so it's okay.

Keep data for a long time.

The traditional hard disk is actually a high-density disk, which is coated with magnetic particles on a hard substrate, and the magnetic field generated by the read-write head changes the noisy changes in the direction of the magnet in the collapse of each track recording unit on the disk for reading and writing. To put it bluntly, it is a 3-inch and 5-inch disk similar to the original, but the density and reliability have been greatly improved.

A hard disk is a data storage device that uses magnetic media to store data on several disk plates sealed in a clean cavity of the hard disk drive. These discs are generally formed by coating the surface of the substrate with magnetic medium, and on each side of the disk, a number of concentric circles with a rotating shaft as the axis and a certain magnetic density as the interval are divided into tracks, and each track is divided into a number of sectors, and the data is stored on the hard disk according to the sectors. There is a corresponding read/write head on each face, so all the tracks in the same position of different heads form the so-called cylinder.

Traditional hard disk reads and writes are addressed by cylindrical, head, and sector (CHS addressing). The hard disk rotates at high speed after power-on, and the head located on the head arm is suspended on the surface of the disk, and can be moved between different cylinders through a stepper motor to read and write different cylinders. Therefore, if the hard disk is subjected to violent oscillation during power-on, the surface of the disk is easily scratched, and the head is also easily damaged, which will bring catastrophic consequences to the data stored on the disk.

The first sector of the hard disk (0 lanes, 0 heads, 1 sector) is reserved as the primary boot sector. There are two main contents in the main boot area: the master boot record and the hard disk partition table.

The Master Boot Record is a program** that boots the operating system installed on the hard disk; The hard disk partition table stores the partition information of the hard disk. When the computer starts, it will read the data of the sector and judge its legitimacy (whether the last two bytes of the sector are 0x55aa or 0xaa55), and if so, jump to execute the first instruction of the sector. Therefore, the main boot area of the hard disk is often the target of virus attacks, which can be tampered with or even destroyed.

Bootable flags: 0x80 bootable partition type flags; 0 means unknown; 1 is FAT12; 4 is FAT16; 5 is the extension partition and so on.

Why can a computer hard drive store data, disassemble and look at the internal structure, it's like alien technology.

The reading and writing methods are similar to those of optical drives.