classification
Up to distinguish data from the storage medium, a hard disk may be divided into mechanical hard disk (Hard Disk Drive, HDD) and SSD (Solid State Disk, SSD), a mechanical hard disk using a magnetic disk to store data, stored by the SSD flash particles data.
From the technical aspects distinguish the type of hard drive is mainly SCSI, IDE, and now the popular SATA, etc. , IDE follows the ATA standard, and popular SATA, it is ATA standard upgrade version; IDE is a parallel device, while SATA is serial port, SATA development purposes is to replace the IDE;
composition
A hard disk, a magnetic head, the disk spindle motor control, the head controller, the data converter, the interface, the control circuit board, part of the buffer, and several components. The BIOS control circuit includes a hard disk, a hard disk and the main chip caching unit; interface unit includes a power supply, the master data from the interface jumpers, etc., the data stored in the disk platter.
technology
Now the hard drive, either IDE or SCSI, are used in "Winchester" technology (except solid-state drives), have the following characteristics:
1. sealing head, the disc and the movement mechanism.
2. The high speed rotation of the fixed and plated smooth disc surface.
3. head moves radially along the disc.
4. head contact start and stop of the disk, but does not work when the flight was in direct contact with the disc. Early designs of disk drive allows the disk heads remain in the top flight a few microns. Some later designs the head flying height in the disk down to about 0.1 [mu] m ~ 0.5 [mu] m, has now reached a level of 0.005 [mu] m ~ 0.01 [mu] m, this is only one thousandth of the diameter of a human hair.
working principle
Properties of the magnetic material to hold information, i.e., electromagnetic conversion, when physics we know that electrical magnetic tape can substance, and the metal cutting motion when the magnetic field generated when the current magnetic field lines. There are many magnetic particles on the disk, when writing data through the head, the head will cause the current magnetic polarization, change direction; read data, the head passes through the conductor region of the magnetic particles will produce electricity. When the disc with a microscope zoom, will see the disk surface irregularities, the raised areas are magnetized, where the recess is not magnetized; where 1 represents the number of projections (magnetized 1), where 0 represent numbers concave . So hard drive can store a binary representation of text, pictures and other information.
Tracks
Each disk surface of each disk is divided into a plurality of narrow concentric rings, such data is stored on concentric rings, this ring will be referred to as a track (Track), each disk may be divided into a plurality of track. Shutdown head stuck in the hard landing zone (Landing Zone), the landing zone used to be located in the areas closest to the hub, does not store any data. (Note that, only the logical structure of the track, in the disk does not really concentric circles), 0 is the outermost concentric track. HDD track density is very high, usually on one side there are thousands of tracks. But not the immediately adjacent tracks, because the magnetization unit spaced too close to each other will have an impact.
Sector
In fact, it is the image of the sector, we have now seen the folded paper fans, paper fan after opening semicircular or fan-shaped, but this sector is formed by each combination of fan bone. On each disk track is concentrically, radially outwardly generating the division lines (Shan Gu), each track divided into a plurality of arc from the center, each arc segment is one sector. The size of each sector is fixed, is 512Byte. Sector is the smallest unit of disk storage.
cluster
The plurality of physically adjacent sectors is called a cluster. The basic unit is the operating system to read and write disk sectors, and file system is the basic unit of cluster (Cluster). Under Windows, just to find a few bytes of a file, right-click on its top and select Properties to see the actual size of the space of two elements, such as size: 15 bytes (15 bytes), space: 4.00 KB (4,096 bytes). Here's footprint is the size of your machine cluster partition, because then a small file takes up space, the basic logic unit is 4K, so takes up 4K. Generally these types of cluster size 4K, 8K, 16K, 32K, 64K and so on. The larger the cluster, the better storage performance, but space is wasted. The smaller clusters of relatively lower performance, but high space utilization. NTFS cluster size of the file system format is 4K.
cylinder
If the hard disk is composed of a plurality of disks, each disk surface is divided into an equal number of tracks, then the disk are all carried out from the outside track number, 0 is the outermost track. With the same number of tracks will form a cylinder, the cylinder will be referred to as cylinders of the disk, to be noted here, hard to read and write data is cylinder, i.e. when the head is first read and write data in the same cylinder from 0 head begins operating, successively in the same cylinder downwardly different disk (i.e., the upper head) is operated, only after all of the same cylinder head is finished before all the write head to the next transfer cylinder, just as the head select through electronic switching to, and must select cylinder by a mechanical switch. Electronic switching over from the mobile to the machine head adjacent the tracks on faster. Thus, reading and writing data performed by the cylinder, without pressing for the disk. Read and write data in this way is to improve the efficiency of the hard disk read and write as much as possible.