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Partitioning a hard disk
What is a partition?
Partitioning a hard disk is made after the physical format of it before formatting and logic. It is to create areas on the disk where the data will not be mixed. This example serves to install different operating systems do not use the same file system. There will be at least as many partitions operating systems using different file systems. In the case of a user of a single operating system, one partition of the disk size may be sufficient, unless the user wants to create several to several readers for example, whose data are separated.
There are three kinds of partitions: primary partition, the extended partition and logical drives. A disc can contain up to four primary partitions (which one can be active), or three primary partitions and one extended partition. In the partition extended the user can create logical drives (ie "simulate" several hard drives smaller).
Let's see an example in which the disk contains a partition and an extended partition of three logical drives (we will thereafter main multiple partitions):
For systems DOS (DOS, Windows 9x), only the primary partition is bootable, so it is the only one on which we can start the operating system.
Called partitioning the process of writing the sectors that constitute the partition table (which contains information on the partition size of it in terms of number of sectors, offset from the main partition, partition types present , Operating systems installed ,...).
When the partition is created, it gives a volume name which will be easily identified.
Master Boot Record
The boot sector (called Master Boot Record or MBR) is the first sector of a hard disk (cylinder 0, head 0, sector 1), it contains the partition table and code, called boot loader, which, once loaded into memory, will allow boot the system.
The program, once in memory, will determine what partition the system will begin and it will start the program (called bootstrap), which will begin operating system present on this score.
On the other hand, this sector of the disk that contains all information on the hard drive (manufacturer, serial number, number of bytes per sector, number of sectors per cluster, number of sectors ,...). This sector is the largest sector of the hard disk, it serves to setup the BIOS to recognize the hard drive. Thus, without it your hard drive is useless, so it is a favorite target for viruses.
The file systems
Throughout this section will be to differentiate the FAT file system of the file allocation table.
FAT file system is used by DOS operating systems (DOS and Windows 95 and Windows NT and OS / 2 that the bear).
The FAT file system is characterized by the use of a File Allocation Table and clusters (or blocks).
The clusters are smaller storage file system of FAT. A cluster is indeed a fixed number of sectors of the disk.
FAT (File Allocation Table) is the core system files. It is located in Sector 2 of 0 to the cylinder head 1 (It is duplicated in another area of precautions in case of accident). In this table the numbers of clusters used are recorded, and where the files are located in clusters.
The FAT file system supports disk or partition size up to 2 GB, but allows a maximum of 65,536 clusters. Thus, whatever the size of the partition or disk, there must be enough of sectors per cluster for the whole disk can be contained in these 65,525 clusters. Thus, over the size of the disk (or partition), the greater the number of sectors per cluster must be important.
The FAT file system uses a root directory (represented on operating systems that use this type of file systems by the sign C:\), to be located in a specific area of the disk drive. This directory stores information on sub-directories and files it contains. For a file, store it thus:
- filename
- file size
- the date and time of last modification of file
- file attributes
- the number of cluster which the file begins
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Multiple Partition
Using multiple partitions
There are, as we have previously seen, three kinds of scores: the primary partitions, the extended partition and logical drives. A disc can contain up to four primary partitions (which one can be active), or three partitions principal and an extended partition. In the extended partition the user can create logical drives (i.e. ensure that we have the impression that there are several hard drives smaller).
Partition
A partition must be formatted logically, and contain a file system for the operating system installed on it.
If you have multiple primary partitions on your disk, one will be active and visible at once, it will depend on the operating system on which you started the computer. By choosing the operating system you run at startup, you choose the partition is visible. The active partition is the partition on which one of the operating system is started at the launch of the computer. Partitions other than where you start will be hidden, which will stop accessing their data. Thus, data from one partition are accessible only from the operating system installed on this score.
Extended partition
The extended partition has been developed to exceed the limit of four primary partitions, with the possibility to create as many logical drives that you want into it. At least one logical drive is necessary in an extended partition, because you do can not store data directly.
Many machines are formatted into a big partition using the entire space available player. This is not the most advantageous in terms of performance and capacity. The solution is to create multiple partitions, which lets you:
- to install multiple operating systems on your hard drive
- save disk space
- to increase the security of your files
- organize your data easier
Let's see what could resemble a system with multiple operating systems:
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