Convert GPT Disks to MBR

This article covers the following topics:


GPT is a part of the EFI standard that defines the layout of the partition table on a hard drive. Forming a part of the Unified Extensible Firmware Interface (UEFI) standard, it is also used for some BIOS systems, because of the limitations of master boot record (MBR) partition tables. Compared to the commonly used Master Boot Record (MBR) partitioning scheme, GPT provides a more flexible disk partitioning mechanism.

GPT (or GUID Partition Table) is the updated version of the MBR table scheme that is available on computers with UEFI/EFI installed (not BIOS).

GPT disks are supported for the following Windows versions:

  • Windows XP 64-bit
  • Windows Vista
  • Windows 7
  • Windows 8
  • Windows 10
  • Windows Server 2003/2008/2008 R2/2012/2016/2019

These disks can also be used to boot Windows from, but only the following 64-bit Windows versions will boot from GPT disks:

  • Windows 10
  • Windows 8
  • Windows 8.1
  • Windows 7
  • Windows Vista
  • Windows Server all editions.

Note that you can boot Windows from GPT only if your machine has UEFI/EFI installed

MBR disks are supported by all Windows versions. Removable disks, such as USB drives, cannot be converted to GPT. These removable disks are always set as MBR.

Convert GPT Disks to MBR

In case you have GPT disks in the cloud storage that need to be restored, and the target restore destination is one of the following:

  • Microsoft Azure
  • AWS EC2
  • Google Compute Engine.

you can enable GPT to MBR conversion since only BIOS boot is supported on these destinations.

Also, conversion from GPT to MBR is required when the target restore destination is an instance with old Windows 32-bit versions. For example, Windows XP 32-bit.

Starting from version 6.3, Backup for Windows introduces a GPT disk conversion to MBR feature for restore plans.

Note that the reverse conversion (MBR to GPT) is not implemented

During the conversion procedure, a sequence of the following actions is performed:

  • A virtual disk is created (VHD)
  • Virtual disk is mounted to a host instance
  • Disk is initialized to MBR
  • A system reserved partition (BIO, size=100 MB) is created
  • Boot files are copied from a host instance to a system reserved partition
  • An in-memory destination image containing a BIOS boot partition and Windows basic data volume from backup storage is created.

Note that the Convert to MBR option is not supported on the following operating systems:

  • Windows 7
  • Windows 2008.

This option is available in the Image-Based restore on the Select Partitions step.