Logical Partition Definition

A logical partition is a a partition that has been created inside of an extended partition.

A partition is a logically independent section of a hard disk drive (HDD). An extended partition is a primary partition that has been designated for dividing up as a means of creating more partitions than the four that are permitted by the master boot record (MBR). The MBR is is a small program that is executed when a computer begins to boot up (i.e., start up) in order to find the operating system and load parts of it into memory.

A primary partition is any of the four possible first-level partitions into which a HDD on an IBM-compatible personal computer can be divided. Only one primary partition can be used as an extended partition, and it can be created from any of the primary partitions.

The sizes of the logical partitions are described at the beginning of the extended partition, not in the MBR. The logical partitions do not need to fill the entire extended partition; that is, empty space can be retained in the extended partition that can be carved up into additional logical partitions in the future if desired.

Linux and other Unix-like operating systems can easily be installed on any partition of sufficient size, regardless of whether it is a primary partition or a logical partition, in contrast to the Microsoft Windows operating systems. Although the MBR can only directly boot the active partition, which must be one of the primary partitions, it can load a boot loader such as LILO (Linux loader) or GRUB (grand unified boot loader), which will, in turn, load an operating system that is on a logical partition.

The term logical partition is an example of the confusing terminology that plagues the computer field. It can initially be confusing to people not familiar with computers because a partition is a logical division of a HDD, and thus at first glance it would seem redundant to say logical partition.

Created April 20, 2006.
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