Linux basic learning disk device internal and external structure
Disk and hard disk are the same name for disk storage system, and the development trend is smaller size, faster speed, larger capacity and safer use. But some friends don't know much about the internal and external structure of the disk, so let's share.
First, the external structure of the disk
1. Disk interface
The interface includes two parts, a power socket and a data interface. The power socket is connected to the power supply of the host to provide power guarantee for the disk. The data interface socket is the channel for data transmission and exchange between the disk data and the motherboard control chip. A data cable is used to connect it with the motherboard IDE interface and the data interface of the disk. The data cable is generally 40 pins and 80 cores. The early data interface has IDE and SCSI, the current mainstream hard disk structure is serial SATA or SCSI interface
2 control circuit board
Most control circuit boards are welded by patch, including spindle speed control circuit, magnetic head drive and servo positioning circuit, read and write electricity, control and interface circuits, etc. There is also a ROM chip on the circuit board, in which the fixed-line program can initialize the disk, perform power-on and start the spindle motor, power-on initial seek, positioning, and fault detection. A high-speed data cache chip of varying capacity is installed on the circuit board , and there is a 2MB cache in this disk.
3 fixed panels
That is, the panel on the front of the disk, which is combined with the bottom plate to form a sealed whole, which ensures the stable operation of the disk and the mechanism. The label on the panel has detailed model and other information. In addition, there is a ventilation hole, its function is to keep the internal pressure of the disk consistent with the atmospheric pressure
Second, the internal structure of the disk
The internal structure of the magnetic disk mainly includes: platter, magnetic head, platter spindle, control motor, magnetic head controller, data converter, interface, cache and other parts. Inside the magnetic disk, the magnetic head and the platter are the core components of the magnetic disk, which are sealed in the sealed cavity of the magnetic disk, including several components such as the flying magnetic head assembly, the magnetic head drive device, the platter, the spindle drive device and the pre-reading and writing control circuit. part.
1. Magnetic head assembly
It consists of three parts: read-write head, transmission arm and transmission shaft. The magnetic head is the most important key link in the magnetic disk technology. In fact, it is a combination of multiple magnetic heads that integrate the process. It adopts a non-contact head and disk structure, and moves on the surface of the high-speed rotating disk after power-on.
The working principle of disk reading data is to use the polarity of specific magnetic particles to record data. When the magnetic head reads data, it converts the different polarities of the magnetic particles into different pulse signals, and uses the data converter to convert these original signals into data that the computer can use. The writing operation is just the opposite .
2. Magnetic head drive
The seek of the disk is achieved by moving the head, and the moving head requires the drive of the device to achieve (mechanical operation). The magnetic head driving device is composed of an electromagnetic coil motor, a magnetic head driving trolley, and an anti-vibration device. The high-precision light-duty magnetic head driving device can drive and position the magnetic head correctly, and can precisely locate the magnetic track specified by the system command in a very short time. .
3. Disk
The platter is the real carrier of the data stored in the disk. Most of the disk platters are made of metal film materials (also glass materials). This metal film has higher storage density, high remanence and high coercivity than the discontinuous particle carrier of the floppy disk. And other advantages, the disk platter is very smooth and flat .
4. Spindle assembly
The spindle assembly includes bearings and drive motors, etc. With the expansion of the disk capacity and the increase in speed, the speed of the spindle motor is also increasing, and manufacturers have begun to adopt the liquid bearing motor technology of the precision machinery industry. The rotational speed of the disk spindle is one of the important references to measure the read and write performance of the disk .
5. Pre-control circuit
The front circuit controls the signal induced by the magnetic head, the speed regulation of the spindle motor, the magnetic head drive and the servo positioning, etc. Since the signal read by the magnetic head is weak, sealing the amplifier circuit in the cavity can reduce the interference of external signals and improve the accuracy of operation instructions .