What Are Extended Partitions And When Would You Use Them?

Extended Partitions
Extended Partitions.

In the past a computer could only have 4 primary partitions. 

Computer users wishing to install Linux would often find themselves in a position where the computer manufacturer had inadvertently used all 4 of the partitions not realising that people might want to create partitions of their own.

Windows would take up one partition and there might be a Windows recovery partition as well. Then the manufacturer will have created a partition for their own recovery software.

This would leave just one primary partition for installing Linux.

In order to run Linux you need at least one partition solely devoted to Linux and because we are talking about older computers you would also need a partition for booting Linux and a third as a swap partition. 

Many people used to set a root partition, a home partition and a swap partition for use with Linux. You could of course have other partitions such as a boot partition, a logging partition and many others.

Those of you who are good at maths will have worked out that it doesn't take much to blow the 4 primary partition limit.

The solution was to split one of the primary partitions into a number of extended partitions. Windows could not boot from an extended partition but Linux was and is more than capable of doing so.

The upper limit for extended partitions is much higher than you are realistically ever likely to use.

Does The Problem Still Exist?

By using extended partitions there wasn't really ever a problem but the question remains are you still locked down to 4 primary partitions.

If you are using an older computer which uses a standard BIOS then you are generally likely to be stuck to the 4 primary partitions.

Modern computers use UEFI and as such they use the GUID partition table (GPT) and this allows you to create many more partitions than you are ever likely to use.

Therefore if you are using an older computer then it is worth knowing that you are locked down to 4 primary partitions but if you are using a modern computer you can easily create many more partitions making it even more simple to dual boot multiple Linux distributions using a single drive.

The main issue with the 4 primary partition limit was the fact that if all 4 partitions were in use then you would need to clear one in order to create extended partitions. 

Everything Has A Limit

In the last part of this guide I will highlight something which you should think about when creating a partition.

Generally people often use the EXT4 partition for running Linux or as a home partition. EXT4 has the following limits:

  • Maximum file size: between 16 gigabytes and 16 terabytes
  • Maximum volume: 1 exabyte

The maximum volume is the key figure here. It is unlikely as a home user that you have a drive containing a single exabyte.

A petabyte is 1000 petabytes which in turn is 1000 terabytes which is of course 1000 gigabytes. My hard drive has single terabyte. I have a NAS drive with 3 terabytes.

Of course disk consumption has risen hugely since the start of the internet age with first images, then music, video, HD video, 3D video and 4K video consuming more and more space.

However we are a long way off the EXT4 limit.

Just be aware that if you have a drive with multiple exabytes of space then you will need to partition it into multiple EXT4 partitions.

Lets compare this to FAT32 which has the following limits:

  • Maximum file size: 2 gigabytes
  • Maximum volume: 2 to 4 gigabytes.

If the world was left on FAT32 then our videos would have to be split across multiple partitions. FAT32 has been replaced by exFAT on devices like SD cards and USB drives.

exFAT has the following limits:

  • Maximum file size: 16 exabytes
  • Maximum volume size: 1 zetabyte

A zetabyte is 1000 exabytes.

Summary

If you are using an older computer with a standard BIOS then you are limited to 4 primary partitions and you are likely to need extended partitions otherwise the limits are more than you could possibly need.

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