What is a hard disk partition?

A hard disk partition is a defined storage space on a hard drive.

Most operating systems allow users to divide a hard disk into multiple partitions, making one physical hard disk into several smaller logical hard disks.

Reasons to Use Hard Disk Partitions

A user may decide to split a hard disk into multiple partitions in order to organize his data more effectively. On Microsoft Windows machines, it is common to store the OS and applications on one hard disk partition and user data on another hard disk partition. When a problem occurs with Microsoft Windows, the OS partition can be completely formatted and reinstalled without affecting the data partition.

A user may decide to split a hard disk into multiple partitions because smaller partitions often have smaller cluster sizes. A cluster size is the smallest chunk of data which a partition can store. A large partition might have a cluster size of 16KB. This mens that a file with one character in it will occupy 16KB of space on the disk. In a smaller partition, that file might only require 4KB to store. This is a useful strategy if you are storing a large number of small files.

A user may have to split a large hard disk into multiple partitions if the hard disk is larger than the partition size supported by the operating system.

Creating Hard Disk Partitions

Most operating system use the 'fdisk' command to create hard disk partitions. Many operating systems also have graphical tools which accomplish the same task, such as EASEUS Partition Master.

Hard Disk Partitions and File Systems

You don't actually store data in hard disk partitions.

You store file systems in hard disk partitions and then you store data in these file systems.

Some operating systems blur the lines between partitions and file systems.

The Partition Table

Partition information is stored in the partition table, a reserved area at the beginning of a hard disk.

Extended Partitions

A standard partition table is only able to store information about four partitions. At one time this meant that a hard disk could have a maximum of four partitions.

To work around this limitation, extended partitions were created.

An extended partition stores information about other partitions. By using an extended partition, you can create many more than four partitions on your hard disk.

The four standard partitions are often called the primary partitions.

Partitions configured into an extended partition are often referred to as logical partitions.

Partition Types

When a partition is created, a special byte of data is written to record what type of partition it is.

Because one hard disk may be shared by multiple operating systems, operating systems tend to agree on the meaning of these values.

The table below lists some of the partition types in use.

Related Articles

• Partition Recovery
• Partition Recovery Software
• What is Partition Boot Sector?
• What is Partition Table?
• What is a hard disk partition?