By Teresa / Last Updated October 28, 2019

MBR or GPT Windows Server

When you first install a disk to a machine, you’ll find it is marked as “unknown” in the Windows Server Disk Management. In order to use the disk, you will need to initialize it as either as an MBR or GPT drive. You may find yourself asking, which one is better for your Server? You should be able to decide which one is better after reading a basic understanding of MBR and GPT.

MBR, which is short for Master Boot Record, is an old and commonly used disk structure. GPT, short for GUID Partition Table, is a modern disk structure which provides a much more flexible approach for partitioning hard disks. GPT, being a modern standard, has many advantages when compared to MBR. GPT is able to support disks larger than 2TB in size, has a theoretically unlimited number of partitions, and has no limitations on the size of partitions. These are the reasons that most users will choose to convert MBR to GPT on Windows Server.

Important: Whilst we can consider GPT to be superior to MBR, there are some limits for converting to GPT on a Windows Server. The computer must be able to boot from UEFI/EFI if you plan to convert an MBR-formatted system to GPT – a 32bit system will not work with a GPT disk, the system must be upgraded to 64bit before the conversion. If you choose to use a GPT disk on a Server which cannot support it, you will not be able to access any of the data.

How can Windows Server Manager assist in an MBR & GPT conversion?

Windows Server offers Server Manager which is a tool that can assist you in converting between MBR/GPT through its graphical user interface. Disk Management also allows you to convert an EMPTY disk to GPT in seconds as does Diskpart in command prompt. If there is partition or volume already on the disk, when you right-click on the disk in Disk Management, you’ll find Convert to GPT Disk grayed out and you have an option to convert it to a Dynamic Disk.

How do you keep the data on your Server intact during an MBR and GPT conversion? Fortunately, Server Manager provides Windows Server Backup which can help you back everything up before deleting. You can follow the detailed steps below.

Convert MBR to GPT without data loss via Windows Server Manager

The below considers converting an MBR-formatted data disk to GPT on Windows Server 2008 as you cannot delete the system partition under the Windows Server environment. Users typically convert their data disks to GPT in order to take full advantage of the disk’s capacity (due to the 2TB limit for MBR). An example would be when a 4TB HDD doesn’t work on a Windows Server.

1. Backup disk volume via Windows Server Backup

You can backup the volume to the local disk or a removable device. If you backup to removable device like your USB flash drive or external hard drive, you should connect it to your Server in advance.

Step 1. Open Server Manager and go Storage -> Windows Server Backup (you can access this utility by typing ‘windows server backup’ in the search box). If you haven’t used this feature before, you will need to install (Server Manager\Features) it first.

Step 2. In the right pane, click on ‘Backup Once Wizard’. Follow the wizard to complete backup settings.

Backup Once Wizard

Step 3. After the backup process completes, go to Disk Management, and delete the existing partitions or volumes.

Delete Volume

2. Convert MBR to GPT on Windows Server 2008 (R2)

Step 1. In Disk Management, right-click the disk and select Convert to GPT Disk.

Convert to GPT Disk Disk Management

Step 2. The conversion process will be completed after a few seconds. You can check the status by right clicking on the disk again, you should find that the option has changed to ‘Convert to MBR Disk’ from ‘Convert to GPT Disk’.

Step 3. Right click the unallocated space to create a new partition with the ‘New Simple Volume’ option, so that you can recover the backed-up data.

Create Volume

3. Recover the backup image via Windows Server Backup

The backup that you just created is displayed in the main window. In order to recover – Click on ‘Recover Wizard’ and follow the steps in the window to complete the file recovery.

Recovery Wizard

As we mentioned before, the above method can’t be applied to converting a system disk between MBR and GPT as you will be unable to delete the “C drive” in the Windows. If you have the Server installation disc or access to the Windows Recovery System you will be able to make a backup of the Server system disk and recover it after converting to GPT.

This process requires you to convert your disk to GPT via Diskpart in Command Prompt. The commands are: list disk -> select disk n -> clean -> convert gpt.

Diskpart Convert GPT

Whilst this method does work, it takes a considerable amount of time and effort. Therefore, we would always recommend using a professional conversion tool (AOMEI Partition Assistant Server Edition). It will allow you to convert between MBR and GPT on Windows Servers without deleting or formatting volumes and partitions on the system disk or data disk. This software simplifies the process with its user-friendly interface suitable for both computer novices and computer experts.

How to convert MBR to GPT on Server 2008 (R2) without formatting partitions?

The next part will show converting an MBR-formatted system disk to a GPT partition table on Windows Server 2008.

Convert MBR to GPT on Windows Server 2008 without losing data

Step 1. Run AOMEI Partition Assistant Server Edition, right click the disk you want to convert, and select “Convert to GPT Disk”.

Convert System Disk to GPT

Step 2. Two windows will appear asking you to confirm the conversion.

OK to GPT System Disk

Step 3. Click “Apply” to execute the pending operation.

Apply to GPT System Disk


  • A reboot is required when the system drive is converted.

  • To boot from a GPT disk, you will need to change Legacy to UEFI.

Change GPT back to MBR on Windows Server with ease

If you want to convert a GPT disk to an MBR disk on Windows Server in the future, you can use the same function in AOMEI Partition Assistant Server Edition. When you right click on a GPT disk, you’ll find the function has changed to “Convert to MBR Disk”. The rest of the steps is the same as above to complete the conversion.

Convert Data Disk to MBR

Tips: After converting to MBR you need to change UEFI/EFI to Legacy if the disk you converted was the system disk.


AOMEI Partition Assistant Server Edition is a reliable and powerful partition tool that was created with Windows Server OS’ in mind. Naturally, it can also be used to convert between MBR/GPT in Windows Server 2012, 2003 (R2), 2016 and 2019 without any data loss.