Web design service - Chapter 28. Disks and Partitions This chapter contains
Chapter 28. Disks and Partitions This chapter contains information for those who simply wish to know more about the technical details underlying their system. It will give a complete description of the PC partitioning scheme. Therefore it will be most useful if you are planning to manually configure your hard drive partitions. 1. Structure of a Hard Disk A disk is physically divided into sectors. A sequence of sectors can form a partition. Roughly speaking, you can create as many partitions as you wish, up to 67 (3 primary partitions and a secondary partition containing up to 64 logical partitions inside): each partition is regarded as a single hard drive. 1.1. Sectors To simplify, a hard disk is merely a sequence of sectors, which are the smallest data unit on a hard disk. The typical size of a sector is 512 bytes. The sectors on a hard disk of n sectors are numbered from 0 to n-1 . 1.2. Partitions The use of multiple partitions enables you to create many virtual hard drives on your real physical drive. This has many advantages: Different operating systems use different disk structures (called file systems): this is the case with Windows and GNU/Linux. Having multiple partitions on a hard drive also allows you to install various operating systems on the same physical drive. For performance reasons, an operating system may prefer different drives with various file systems on them because they may be used for completely different things. One example is GNU/Linux which requires a second partition called Swap. The latter is used by the virtual memory manager as virtual memory. Even if all of your partitions use the same file system, it may prove useful to separate the different parts of your OS into different partitions. A simple configuration example would be to split your files into two partitions: one for your personal data, and another one for your programs. This allows you to update your OS, completely erasing the partition containing the programs while keeping the data partition safe.