3TB Shows 746GB on Windows Server, What Should I Do to Solve It?

I have a problem; we have a 3TB SATA disk on the carry disk, connected to the physical server via USB. The problem is that only 746GB is read. The server is Windows Server 2012 R2, Windows 10 also has this problem. Will it be firmware? Any ideas?

Best Answered by

Sherly· Answered on Jul 04, 2025

Generally, this kind of problem is because your disk is initialized as MBR. Partitions on the MBR have a size limit. You can convert MBR to GPT in CMD using the Diskpart tool. But you need to know that Diskpart deletes all files and folders from your hard drive when changing the disk to GPT. So if you have important data, remember to back it up in advance. Next, I will show you how to use CMD to convert MBR to GPT to solve your problem.

1. Type CMD in the search box. Right-click on Command Prompt and select "Run as Administrator."

2. Open Command Prompt, type DiskPart, and press Enter.

Then, use the commands below one by one:

  • list disk
  • select disk * (Replace * with the target disk number)
  • clean
  • convert mbr
  • exit

As you can see, the "clean" command will delete all the data on your disk, so I used to turn to EaseUS Partition Master Server.

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The third-party software helps convert MBR to GPT without losing data; hence, if you are new to computing, EaseUS Partition Master Server is a better choice for avoiding data loss.

If your issue still exists, it may be because your USB-SATA interface is old and doesn't support it. I've seen this before.
Get a new USB3 - SATA enclosure and move the drive into it. 

Sincerely hope my answer can help you out.

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