Primary Partition, Logical Partition and Extended Partition (Disk Partition Basic)

A disk partition is a defined storage space on a hard drive. All Windows operating systems can let users divide a hard disk into multiple partitions, in this way, making one physical hard disk into several smaller logical partitions.

December 23, 2014

Primary Partition, Logical Partition and Extended Partition (Disk Partition Basic)

About Partition

A disk partition is a defined storage space on a hard drive. There are three kinds of partitions: primary partition, extended partition and logical partition. All Windows operating systems can let users divide a hard disk into multiple partitions. In this way, users can allocate one physical hard disk into several smaller logical partitions. To store classified data, multiple partitions on a disk can organize his data more effectively. On the disk of a computer, the OS was installed in one partition and the other partitions are created to store user data, documents or games. The benefit of such arrangement is when a problem occurs to Windows system, the OS partition can be totally overwritten and reinstalled, and this does not affect the data partition.

Some users may split a hard disk into multiple partitions because smaller partitions offer 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 64KB. This means that a file even with one word in it will also occupy 64KB of space on the disk. In a smaller partition, that file might only require 2KB to be stored. This is a useful policy if you need to save a large number of small files. Yet, too small clusters will generate many disk fragments during data read-write process. Thus, it’s better to choose a proper cluster size according to your own condition. 

You can create, delete and format partition through using the diskpart.exe command. Many operating systems also have graphical tools which accomplish the same task such as Partition Assistant, which is a free partition manager. It not only can partition on a disk, but also resize/move a partition to adjust the size of the partition to optimize disk space usage.

By Microsoft:

  • Partition is a part of a computer hard disk that functions like a separate disk. Separate, formatted partitions share your computers’s memory and storage space. Partitions allow you to install more than one operating system on the computer.

  • Volume is a storage area on a hard disk that is formatted with a file system. Volumes have drive letters assigned to them. A single hard disk can have multiple volumes while a single volume can also span multiple hard disks.

Tip:Usually, “partition” and “volume” can serve as alternative to each other when we describe something about computer for they functions nearly the same. The biggest difference is that “partition” is a term used for basic disk while “volume” is for dynamic disk; and Windows system can’t be installed on dynamic volumes.

The following is Disk Partition Related Glossary

Primary Partition and Active Partition:

What is primary partition? A primary partition is in which an Operating System can be installed. One MBR hard disk may contain a maximum of 4 primary partitions. An active partition is based on primary partition. Any one of the 4 primary partitions can be set as active partition. Since there can be 4 primary partitions with 4 different Operating Systems installed, one of the partition that is marked active is used for the initial booting. The active partition contains the boot loader (such as ntldr or bootmgr) to load operating systems from a disk.


  • Primary Partition: A primary partition contains one file system. In DOS and all early versions of Microsoft Windows systems, Microsoft required what it called the system partition to be the first partition. All Windows operating systems from Windows 95 onwards can be located on (almost) any partition, but the boot files (io.sys, bootmgr, ntldr, etc.) must reside on a primary partition. However, other factors, such as a PC's BIOS (Boot sequence on standard PC) may also impose specific requirements as to which partition must contain the primary OS. (By Wikipedia)

  • Active Partition:The active partition is the partition where theboot flagis set. DOS and Windows allow only one boot partition to be set with the boot flag. (By Wikipedia)

  • If there is only one partition installed system on a hard disk, then it is automatically activated. If there are more than one system (more than one system partition), users can manually set a system partition as active partition

Extended Partition and Logical Partition:

Because the primary only can be created four maximum, this need to use extended partition to break the limitation of 4 partitions. In an Extended Partition you can create unlimited logical drives. You can store data in the logical partitions similar with primary partition, but the extended partition is not used to store data, because the Extended Partition is used to hold logical partitions, at the same time, there can only be one extended partition on a single disk.


  • Extended Partition: An HDD may contain only one extended partition, but that extended partition can be subdivided into multiple logical partitions. DOS/Windows systems may then assign a unique drive letter to each logical partition.(By Wikipedia)

  • Logical Drive: Also called logical partition. A volume created within an extended partition on a basic disk. A logical drive can be formatted and assigned a drive letter, but cannot host an operating system. (By Microsoft) fortunately, you canconvert logical to primary.

  • MBR and GPTOn a MBR disk, there can only be maximum 4 primary partitions or less than 4 primary partitions plus one extended partition. On a GPT disk, there is no concept of primary or logical, thus, the primary partition limitation does not exist. 

The Rules of Partitioning a Hard Drive

A hard disk drive must be partitioned before you can use it. There are some rules as follows:

  • A maximum of four primary partitions can be created on any MBR hard disk. The limitation of four primary partitions is that when one primary partition is applied to the system the master boot record is structured.
  • There is only one primary partition can be designated as active partition and this partition is used to boot system.
  • BIOS will only recognize the active partition for loading operating system. Other partitions can’t be recognized.
  • To break the limitation of at most 4 primary partitions, you have to create 3 or less primary partitions plus an extended partition and there is only one extend partition.

What is Partition Table?

Partition Table is a storage space which records some information about primary, extended and logical partitions. Further, the create/delete/resize of any partition all will modify the partition table to reflect the changes permanently. If partition table is crashed by virus or other stuffs, you partition will lost, so the table is extremely important.

Download Partition Assistant Standard Edition (FREEWARE)