Compared to an MBR (Master Boot Record) disk, a GPT (GUID Partition Table) disk has many advantages. For example, it can overcome the 2TB space limit and the restriction of having a maximum of 4 Primary partitions on a disk. That means you can create partitions larger than 2TB and more than 4 Primary partitions on a GPT disk. It is common to use an over-4TB disk for a server; if you do not convert the MBR disk to GPT, the remaining disk space will be shown as Unallocated, and it cannot be used to create new volumes or extend other partitions. Many people ask if it is possible to convert MBR to GPT in Windows Server 2016 without losing data. The answer is yes. This article introduces 2 ways to convert an MBR disk to GPT in Server 2016 with the MBR2GPT command and a third-party MBR to GPT converter.
Convert MBR to GPT in Windows 2016 Server with a Disk Converter
- Download this tool, right-click the leftmost area of the MBR disk, and select "Convert to GPT Disk".
- Simply click "Yes" to confirm, then a pending operation is added.
- Click Apply on the top left to execute, and you are done. (All operations before clicking "Apply" only work in virtual mode.)
Watch the video to see how to convert an MBR disk to GPT in Windows Server 2016:
To convert MBR to GPT in Windows Server 2016 without an operating system, it is very easy and fast to accomplish by following the steps above. But for an MBR disk that has an operating system, you should pay attention. If anything goes wrong when converting the disk from MBR to GPT, the system may be damaged.
Before converting MBR to GPT in Server 2016 with an operating system, make sure your server motherboard supports UEFI booting. If it does, make a full system backup and run a safe MBR to GPT converter. Few third-party software programs can ensure 100% safety when converting a system MBR disk to GPT. It is suggested to convert a Server 2016 system disk with the MBR2GPT command. This tool is provided by Microsoft and is much safer than third-party software.
Change MBR to GPT with the MBR2GPT.exe Command in Server 2016
MBR2GPT.exe runs from the command prompt. On Windows Server 2019 and Windows 10 (1703 and later versions), you can convert an MBR system disk to GPT with this command in Windows. But to run MBR2GPT in Windows Server 2016, you need to create bootable media with the Windows Preinstallation Environment (Windows PE).
The MBR2GPT command can only convert the system disk. To convert a data-only disk from MBR to GPT, follow the steps above.
There are 3 major steps to convert MBR to GPT in Windows Server 2016 with the MBR2GPT command:
Step 1: Check Disk Partition Configuration
Before any changes to the disk are made, MBR2GPT validates the layout and geometry of the selected disk. If any of these checks fail, the conversion will not proceed.
- There can be a maximum of 3 Primary partitions on this MBR disk.
- One of the partitions is set as "Active" and is the system partition.
- The disk does not have any Logical partition.
- All file systems of the partitions on this MBR disk are supported by Windows.
Step 2: Change Disk Partition Layout If Needed
If your disk partition configuration does not meet the requirements, when the MBR2GPT command checks the geometry, it will report an error: "Validating layout, disk sector size is: 512 bytes Disk layout validating failed for disk 0", "MBR2GPT: Conversion failed".
On most system disks in a Windows 2016 server, there is a System Reserved partition, a C: drive (for the OS), and a D: drive. If all these 3 partitions are Primary, you can convert this disk successfully.
- If there is a Logical drive, convert it to Primary (without data loss).
- If there is a fourth partition such as E, move it to another disk, no matter whether it is Primary or Logical.
- If there are any partitions not supported by Windows, move the files to another place and delete the partition.
Extend the System Reserved Partition (Optional)
Unlike the System Reserved partition on an MBR disk, an EFI system partition (ESP) will be created on a GPT disk. MBR2GPT will shrink the System Reserved partition first. If there is not enough free space in it, MBR2GPT will shrink the C drive instead. In that case, the EFI partition will be created on the right of the C drive.
In the command prompt, it clearly shows the steps of what MBR2GPT does when converting an MBR disk to GPT. As you can see, MBR2GPT first tries to shrink the System Reserved partition; if it cannot be done, it shrinks the OS partition C instead.
Before converting MBR disk:
After converting to GPT disk:
As you can see in the screenshot, a 100MB EFI system partition is created behind the C drive after converting Disk 0 to GPT. When right-clicking it, all options are grayed out. That means Disk Management cannot do anything to the EFI partition.
NIUBI Partition Editor can shrink, extend, and move the EFI partition in Windows Server 2016. If you want to create the EFI partition on the left and keep the C and D drives contiguous, you should extend the System Reserved partition before converting. If having the EFI partition on the right is not a problem for you, simply ignore this step.
Download this tool and follow the method in the video to extend the System Reserved partition (it is enough to extend 1 or 2GB):
Step 3: Run the MBR2GPT Command to Convert MBR to GPT in Windows 2016 Server
① Download the Windows Server 2019 ISO and create a bootable DVD disc or USB flash drive with a Windows built-in or third-party tool.
② Boot from this bootable media, simply click Next in the first Windows Setup window, then click "Repair your computer" on the bottom left corner of the next window.
③ Click "Troubleshoot" in the next window, then click Command Prompt.
④ Just input 2 commands to complete the conversion:
- cd..
- mbr2gpt /convert
Within several minutes, this MBR disk will be converted to GPT. If the System Reserved partition was extended to 1GB beforehand, MBR2GPT will shrink the System Reserved partition successfully. Restart the server and boot into UEFI; Disk 0 will be converted to GPT, and the EFI system partition will be created on the left side of the C drive.
Besides converting an MBR disk to GPT in Windows Server 2016/2019/2022/2025 and previous Server 2012/2008/2003, NIUBI Partition Editor helps you convert a partition between Primary and Logical, and convert NTFS to FAT32 without losing data. It also helps you shrink, extend, move, and merge partitions to optimize space usage, and clone a disk partition to migrate the Operating System and data. You can also create, delete, format, convert, defrag, hide partitions, and much more.
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