How to Convert MBR to GPT In Windows Server 2016

by Andy, Updated on: October 1, 2021

GPT (GUID Partition Table) disk has many advantages than MBR (Master Boot Record) disk, for example: overcome the maximum 2TB partition and 4 Primary partitions limit. That means, you can create larger than 2TB partition and more than 4 Primary partitions in single GPT disk. It is common to use over 4TB disk for a server, if you do not convert MBR disk to GPT, the rest disk space will be shown as Unallocated and it can't be used to create new or extend other partition. Many people ask if it's possible to convert MBR to GPT in Windows Server 2016 without losing data. The answer is yes. In this article, I'll introduce 2 ways to change MBR disk to GPT with Windows MBR2GPT command and third party MBR to GPT converter in Server 2016.

Convert MBR to GPT in Windows 2016 server with converter

  1. Download NIUBI Partition Editor, right click the front of the MBR disk and select "Convert to GPT Disk".
  2. Simply click Yes to confirm, then a pending operation is added.
  3. Click Apply on top left to execute, done. (All operations before clicking Apply only work in virtual mode.)

Watch the video how to convert MBR disk to GPT in Windows Server 2016:

Video guide

To convert MBR to GPT in Windows Server 2016 without operating system, it is very easy and fast to accomplish by following the steps above. But to the MBR disk that has operating system, you should pay attention. If anything goes wrong when converting MBR disk to GPT, system may be damaged and data may be lost.

Before converting MBR disk to GPT in Server 2016 with operating system, make sure your server mother board supports UEFI. If it does, make a full system backup and run safe MBR to GPT converter. Few third party software can ensure 100% safety, the best option to convert Server 2016 system disk is running Windows MBR2GPT command, this safe tool is provided by Microsoft.

Change MBR to GPT with MBR2GPT.exe in Server 2016

MBR2GPT.exe is running from command prompt. On Windows Server 2019 and Windows 10 (1703 and later versions), you can convert 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 Windows Preinstallation Environment (Windows PE). Note: MBR2GPT command can only convert system disk. To convert data only disk from MBR to GPT, follow the steps above.

There are 3 major steps to convert MBR to GPT in Windows 2016 server with MBR2GPT command:

Step 1: Check disk partition configuration

Before any change to the disk is made, MBR2GPT validates the layout and geometry of the selected disk, if any of these checks fails, the conversion will not proceed.

  1. The disk is currently using MBR
  2. There is enough space not occupied by partitions to store the primary and secondary GPTs: 16KB + 2 sectors at the front of the disk and 16KB + 1 sector at the end of the disk.
  3. There are at most 3 primary partitions in MBR partition table
  4. One of the partitions is set as active and is the system partition
  5. The disk does not have any extended/logical partition
  6. The BCD store on the system partition contains a default OS entry pointing to an OS partition
  7. The volume IDs can be retrieved for each volume which has a drive letter assigned
  8. All partitions on this MBR disk are recognized by Windows.

In general, you just need to pay attention to number 3, 5 and 8. If your disk partition configuration meet the requirements, jump to Step 3 to convert. Otherwise, follow Step 2 to change your disk partition.

Step 2: Change disk partition if needed

If your disk partition configuration doesn't meet the requirements, when MBR2GPT command check the geometry, it will reports error - "Validating layout, disk sector size is: 512 bytes Disk layout validating failed for disk 0", "MBR2GPT: Conversion failed".

Partition layout

In most of Windows 2016 server system disk, there are System Reserved, C: (for OS) and D drive. If all these 3 partitions are Primary, you can convert this disk successfully.

  1. If D is Logical drivel, follow the step to convert it to Primary (without data loss).
  2. If there is fourth partition such as E, move it to other disk no matter it is Primary or Logical.
  3. If there are any Windows non-support partition, move files to other place and delete this partition.

Extend System Reserved partition (optional)

For Windows to remain bootable after the conversion, an EFI system partition (ESP) must be in place. MBR2GPT will shrink the System Reserved partition first. If there is not enough free space in it, MBR2GPT will shrink C drive. In that case, the EFI partition will be created on the right side of C drive.

In the command prompt, it shows clearly the steps what MBR2GPT do when converting MBR disk to GPT. As you see, MBR2GPT first try to shrink the system reserved partition, it can't be done, so it shrink the OS partition C instead.

MBR2GPT

Before converting MBR disk:

Before converting

After converting to GPT disk:

After converting

As you see, 100MB EFI system partition is created behind C drive after converting Disk 0 to GPT. When right clicking it, all options are grayed out. That means, Disk Management cannot resize or move EFI partition.

NIUBI Partition Editor can shrink, extend and move EFI partition in Windows Server 2016. If you want to create EFI partition on the left and make C, D drive to be contiguous, you should extend system reserved partition. If EFI partition on the right is not a problem to you, simply ignore this step.

Download NIUBI Partition Editor and follow the method in the video to extend the System Reserved partition (it's enough to extend 1 or 2GB):

Video guide

Step 3: Run MBR2GPT command to convert MBR to GPT in Windows 2016 Server:

Download Windows Server 2019 ISO and create bootable DVD disc or USB flash drive with Windows built-in or third-party tool.

Boot from this bootable media, simply click Next in first Windows Setup window, then click Repair your computer on bottom left corner of next window.

Setup window

Repair computer

Click Troubleshoot in next window, then click Command Prompt.

Troubleshoot

Command Prompt

Just input 2 commands to complete converting.

  1. cd..
  2. mbr2gpt /convert

Within several minutes, this MBR disk is converted to GPT. I've extended system reserved partition to 1GB on my server, this time MBR2GPT shrink the system reserved partition successfully. Restart server and boot to UEFI, disk 0 is converted to GPT and the EFI system partition is created on left side of C drive.

MBR2GPT command

Convert successfully

Besides converting MBR disk to GPT in Windows Server 2016/2019 and previous Server 2012/2008/2003, NIUBI Partition Editor helps you convert partition between Primary and Logical, convert NTFS to FAT32 without losing data. It also helps you shrink, extend, move and merge partitions to optimize space usage, clone entire disk or single partition to migrate Operating system and data, create, delete, format, convert, defrag, hide partition and much more.

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