Cylinder

The basic components of disk are platters made of hard metal materials and coated with magnetic media. And disks with different capacity have different amounts of platters. Ever platter has two sides and both can record information. Platters are divided into sectorial areas and every area is called a sector that can store information of 128*2N (N=0, 1, 2, 3) bytes. In DOS, every sector is 128*22=512 bytes. Take center of platter surface as the center of the circle and the concentric circles with different radiuses are called tracks. Disk is composed of a group of platters piling up. And every platter is divided into tracks with equal number and from outside to inside the tracks are numbered from 0. Tracks having the same number constitute a cylinder called disk cylinder. The total number of disk cylinders is equal to that of tracks. As every platter has its own head, the number of platters is equal to that of heads. And the CHS of disk contains cylinder, head and sector. If the numbers of CHS are known, the disk capacity can be calculated: Capacity = cylinders* heads* sectors *512B

The Relationship between Cylinders and Disk Read-Write
Heads in every cylinder are numbered from 0 in super-incumbent way. Data read-write is according to cylinders. When the head reads and writes data, it will start from head 0 in the same cylinder and operate in turn down in different platters (heads) of the same cylinder. Only all the heads of one cylinder complete the read and write process can the head move to next cylinder. Because the head is chosen through electronic switch and the cylinder is chosen through mechanical switch. The electronic switch is very fast. Its speed is faster than that of moving to the near track. Therefore, data read-write is according to cylinders instead of platters. It means that when a track is full, data write is continued in the next platter of the same cylinder. And only the cylinder is full, it is moved to the next cylinder and data write is started from Sector 1. It is not in the way of starting from a track in a platter and starting from Track 0 in next platter when the flatter is full. And data read is operated in the same way, which improve the the efficiency of disk read-write.
The cylinder number does not only depend on the width of every track, but also the step pitch between tracks. And the step pitch is decided by positioning mechanism. Usually the cylinder number can not be got from equipment parameters. And relevant disk management software can be applied to obtain the corresponding information. MiniTool Partition Wizard is a good disk partition management software. By applying this software, users can do more operations and know relevant parameter information of disk.



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