Basic knowledge about Hard Disks

1. physical composition of the hard disk

The common hard disks are 2.5 inch and 3.5 inch, which are used for Laptops and Desktops respectively. In terms of physical composition, the hard disk is composed of disc, mechanical arm, head and spindle motor. In actual operation, the Spindle Motor rotates the disc, and the mechanical arm is stretched to allow the head to read and write on the disc. The capacity of a single disk is limited, so there are more than two disks in the hard disk.

2. Data on disks

The actual data is written on a disk with magnetic material. How is the data written on the disk written?

The whole disk seems to have multiple circular images drawn from concentric circles. The smallest unit of storage for the hard disk is separated by radiation from the center of the Disk: Sector (sector ), the size of each slice is fixed to 512 bytes, and a circle formed by the slice becomes a track ). If multiple disks exist, the same magnetic track on all disks can form a cylinder ). The cylinder is the smallest unit when we split the hard disk.

Next we will talk about the calculation of hard disk capacity. The formula is as follows: Number of headers * Number of cylinders for each header * Number of slice contained in each cylinder * Capacity of the slice. The simple syntax is: Head * cylinder * sector * 512 bytes.