MBR and GPT Based Hard Drive Partitions

FOR~GO
(For Geeks Only)
By Joe Callison
6 November 2017

Windows on a UEFI-based device must format the hard drive for Windows with a GUID partition table (GPT) file system instead of a Master Boot Record (MBR) file system. Besides the EFI System Partition on a GPT drive, it will have a Microsoft reserved partition (MSR) to help with partition management, the Windows partition, and a Recovery tools partition for the Windows Recovery Environment tools image, which also supports booting partitions with Windows BitLocker Drive Encryption, if used. Additional OEM-utility partitions or data partitions could optionally be present. 

Windows supports 128 partitions on a GPT drive compared to a maximum of 4 basic partitions on an MBR drive, though a secondary structure of extended partitions can be used and subdivided into multiple logical drives on the MBR drive. Each partition on a GPT drive can have a maximum of 18 exabytes (about 18.8 million terabytes) compared to a maximum of 2 terabytes for an MBR drive. In comparison to MBR, GPT supports more partitions, larger partition sizes, primary and backup partition tables, CRC32 fields for improved data structure integrity, and 36-character partition names. To prevent legacy disk management utilities that operate on MBR from mistakenly identifying a GPT drive as unpartitioned, a protective MBR area exists that will make it appear to have an MBR partition.

The basic disk partition layout for an MBR drive with Windows is:

An example of an MBR partition layout with more than 4 partitions is:

The basic partition layout for a GPT drive with Windows is:

An example of a GPT partition layout with more than 4 partitions is:

For more in-depth information on MBR and GPT-based partitions see:

https://docs.microsoft.com/en-us/windows-hardware/manufacture/desktop/configure-biosmbr-based-hard-drive-partitions

https://msdn.microsoft.com/en-us/library/windows/hardware/dn640535(v=vs.85).aspx