A hard disk is a data storage device based on the principle of magnetic recording. It records data on hard (aluminum or glass) plates or disks coated with a layer of ferromagnetic material.
Components of a hard drive
1 - Permanent magnet
2 - Head assembly commutator
3 - Rotating frame of read/write heads
4 - Actuator of disk rotation
5 - Disks (one or more)
6 – Read/write heads
7 - Integrated circuit
8 - Chassis
The integrated circuit synchronizes the hard disk drive with your computer, manages all processes, and keeps the rotation speed constant.
The drive spins the disk from 5,400 to 15,000 rpm. The spin rate of the drive depends on the type and quality of the drive's hardware. This affects how fast it runs.
The read/write heads write and read information, and a rotating frame moves them across the area of the rotating disk 60 times per second. The end of the read/write heads is split to handle multiple disks at the same time.
In operation mode, the read/write heads do not touch the surface of the disks due to the airflow. The distance between the read/write head and the disks is only a few nanometers. The lack of physical contact with the surface increases the drive's life.
In non-operational mode, the read/write heads are in a safe area where no contact with the platter surface is possible.
Data Storage
1 - Sectors
2 - Tracks
Data is stored in narrow tracks on the surface of a disk. Over 200,000 of these tracks are generated during disk production. Each track is divided into sectors. A map of tracks and sectors allows the drive to determine where to write to and read from.
The disk's surface is coated with a ferromagnetic film that stores all the information. The read/write head magnetizes a microscopic area (cell) on the disk's surface and adjusts the magnetic moment of such a cell to one of the states zero or one. A bit refers to each of these zero or one states. The bit value corresponds to the value of the magnetic field: plus or minus.
For example, a high-quality picture occupies about 29 million such cells and is distributed over twelve different sectors. This is just a very small area on the surface of the disk.
Thus, according to the law of magnetism, the thin ferromagnetic film of a disk can retain gigabytes of information.
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