By Lucas / Last Updated March 4, 2022


“Hello there. I am getting trouble in using WD Black 4TB hard drive on my Windows Server 2012. I bought this hard drive to store some backups only to find the 4TB hard drive showing up as 2TB in Server 2012 and no more space available. Can someone explain how should I proceed to get the unallocated space on 4TB hard drive? Does my Server unable to work with the large capacity disk?

By the way, another 3TB disk is on the way home with which I plan to replace my current pretty old hard drive for my Server. If that is the problem, I probably should cancel the 3TB drive and re-order a smaller one. But I don’t want to. Please help!”

4TB HDD not working on Windows Server 2012 due to MBR limit

From the description of above example, it could be the problem of MBR limit. When you first install the disk to machine, it will ask you to initialize disk to MBR or GPT, two different partition styles with different performances.

The MBR has a 2TB limit due to its partition table and fortunately GPT table makes up for this. If you initialized the 4TB disk to a wrong partition table at the beginning and the disk not showing up correctly, you can easily solve this problem by changing it to GPT again.

However, there is one more thing you may need to pay attention to before MBR to GPT conversion. If want to install Windows Server 2012 OS on GPT partition table and boot there, make sure your computer supports EFI or UEFI boot mode. If you just use the 4TB disk as extra storage, there is no requirement for the motherboard of your machine.

Convert MBR to GPT to solve 4TB HDD only showing 2TB on Server 2012

It is nice to know that Windows Server 2012 provides utilities, Disk Management and Diskpart, to help you convert empty disk from MBR to GPT. That is to say, you need to clean up all partitions or volumes on the 4TB disk before converting.

The quickest way to access Disk Management in Windows Server 2012 is to right-click the bottom-left-corner on the desktop to open Quick Access Menu. Disk Management is listed there. Connect the 4TB drive to your Server 2012 first.

1. Convert to GPT with Windows Server built-in tools

To do with Disk Management in Server 2012, right click any existing partition and select “Delete Volume”. Repeat this step until the disk is empty. Then, right click the disk and select “Convert to GPT Disk”. The converting process will be done in a few seconds.

Convert To Gpt Clickable Server

To do with Diskpart in CMD, press+key combo, type “diskpart” to start Command Prompt. Input following commands in order and each order comes with an. “list disk > select disk n >clean > convert gpt > exit”. Where “n” is the number of the 4TB hard drive you want to convert to GPT.

Diskpart Convert To Gpt

1. All data will be wiped out during the conversion. So back up important files to safe place before you start.
2. If install on 4TB hard drive and get GPT error on Server 2012 (R2), press+to start Command Prompt.

2. Convert to GPT from MBR without deleting partitions/data loss

Since Windows Server snap-in tools will convert empty disk only to GPT, it is hard to convert MBR-formatted system disk to GPT with them. Under this circumstance, it is a wise move to do it with 3rd-party partition manager. AOMEI Partition Assistant Server is such a great MBR & GPT conversion tool that allows you to convert system and data disks to desire partition table without deleting any partitions on Windows Server 2022/2019/2016/2012 (R2), Server 2003, etc.

1. Install and run AOMEI Partition Assistant. Right-click the 4 TB hard drive that not working on Server 2012 and select “Convert to GPT Disk”.

Convert 4tb To Gpt

2. Confirm the operation.

Ok 4tb Gpt

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

Apply 4tb Gpt

1. If system involved, a reboot is required. To convert to GPT without booting Windows Server 2012 via this software, make a bootable USB/CD/DVD in advance.
2. You can convert GPT to MBR on Server 2012 with the same software in the future, if you wish to.
3. Data loss might be caused by inappropriate operations, so please backup files you care most just in case.
4. This method can also used to solve 4TB HGST SATA drive only shows 1.62 TB on Windows Server 2012.

Other possible reasons for 4TB disk not working and corresponding fixes

Obviously, there are many other factors that caused 4TB HDD not available for Server 2012 and other Windows OSes. To sum up, four main components are listed below.

System 32-bit version limitation: All Windows 32-bit systems do not support boot from UEFI or EFI mode. As a result, to use 4TB HDD as system disk, you need to upgrade 32-bit to 64-bit or x86 to make it available for EFI/UEFI boot. As covered before, to use 4TB hard drive as data disk only, neither boot mode important.

Software Filter Drive affecting: If 4TB external USB drive not recognized by Server 2012 R2 after convert to GPT, it could be the problem of Filter drive of some certain backup software. You can uninstall the backup software to test, or contact the backup software support to consult the problem.

Server Controller Card limitation: When motherboard is UEFI-supported and the 4TB is GPT-formatted, you can still get trouble, for example, 4TB HDD not working on Windows Server 2003 SP2. In that case, it could be that the Controller Card is unable to handle GPT +2TB disk. Upgrade to a more compatible one.

Server driver is out-of-date: Work 4TB USB drive with, for example Dell PowerEdge T320, if the Server driver is not up-to-date, the 4TB external disk will not be recognized. You can download the latest version from their manufacturer website to solve this issue.


When you find 4TB HDD not working on Windows Server 2012, have a clear understanding on your own situation because different causes have different solutions.

Apart from converting between MBR and GPT, AOMEI Partition Assistant Server also comes with many other amazing functions: move partition, merge partitions, allocate free space, split partition, move Windows Server to new hard drive, clone hard disk, and more. To use such kind of software on unlimited computers within one company, the Unlimited edition is worth your trying.