(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:
|System||OEM-Utility||Utility or Data||Extended Partition
Windows – Recovery – Data (logical partitions)
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: