Partitioning

Partitioning -What exactly is it?

While the term has fallen out of common practice, the act of "partitioning" a hard disk is really a low level format in essence. When you create the "partition", you are setting up physical parameters of the drive itself, actually drawing out all of the sectors, intersector and intergap and sector header and trailer information. This step is where the master boot record, and the boot record backups are setup as well. The file system and information required by the operating system to manage the disk is done later during the high level format. This is the actual "format" command, which will be covered later on.

Before moving on to the actual O/S and software installation process, you will of course first need to partition and then format your new hard drive before you can store any information on it. As mentioned above, when you partition the drive, you are setting up the physical parameters of the drive. While the term partitioning seems to infer that you ~must~ create multiple sections (or parts), you are actually able to create a single partition using the entire size of the disk. The only absolute is that at least one partition must exist on the drive, (regardless of whether it uses all the available disk space or not, but in the case of the latter you would be wasting disk space for no reason) in order for the system to assign it a drive letter and for you to be able to format and store data on it. Also, the primary hard drive (whether SCSI or IDE) must be marked as "active" in the partition software in order to be bootable. More often than not, you will not have to worry about making the primary partition active; FDISK will do that for you automatically.

All of the information about the Partition(s) are stored in the "master partition boot sector", and is always located in the first sector of the disk at cylinder 0, head 0, sector 1 (C:0 H:0 S:1).

Extended and logical partitions

DOS and FAT (File Allocation Table) were originally designed to support up to 24 partitions on a single hard disk (with each partitions being designated a letter from C to Z), but the partition table in the master boot record can only have a maximum of four partition entries. To work around this, FDISK allows you to create one extended partition, and up to 23 logical partitions within that extended partition, allowing each to be assigned a Drive letter, and to be treated by the computer as a separate physical device. All information about the logical partitions is stored within the extended partition, and only the primary and Extended partition information are stored in the MBR. This means that only two partition entries will ever exist in the master boot record for any one drive, those of the primary (boot) partition and the extended.