Track, sector, and cylinder

Track, sector, and cylinder

When a disk is rotated, if the head is kept at a position, each head will draw a circular track on the disk surface, which is called a track. Figure 1 shows a disk and a head enlargement diagram (the figure exaggerated the size of the head relative to the disk, so the width of the track is also enlarged ). These channels are invisible to the naked eye, because they are only some of the magnetization of the disk surface in special ways, and the information on the disk is stored along such a track. The adjacent channels are not closely related to each other. This is because magnetic fields affect each other when the magnetization are too close, and it also brings difficulties to the reading and writing of the head. A 3.5 inch MB Floppy disk has 80 tracks on one side, while the track density on the hard disk is far greater than this value. Usually there are thousands of tracks on one side.

Each track on the disk is divided into several arc segments, which are the disk sectors. Each sector can store 512 bytes of information. When the disk drive reads and writes data to the disk, the Unit is slice. 3.5 inch MB Floppy disk, each track is divided into 18 sectors.

A hard disk is usually composed of a group of overlapping disks, each of which is divided into equal tracks and numbered from "0" at the outer edge, from the enlarged hard disk structure diagram in Figure 2, we can see that a magnetic track with the same number forms a cylindrical disk. The number of cylinders on a disk is equal to the number of tracks on the disk. Because each disk has its own head, the number of disks equals to the total number of cores. The so-called hard disk CHS (cylinder), head (head), Sector (sector), as long as you know the number of CHS of the hard disk, you can determine the capacity of the hard disk, hard disk capacity = Number of cylinders X number of magnetic heads X number of sectors x B.