I bought new 250GB SSD drive and 3TB HDD and i want to use it with windows 8.1. I have installed windows on the SSD drive but i cant use my 3TB with its full capacity.

What I want is to split my 3TB HDD drive into two 1.5TB disks D:, E:.

This is what i have:

enter image description here

As you can see, system ignores 3TB drives and only allows me to create disk with 1.99TB but that is not what i want. Disk Manager shows rest of disk space as Unallocated. Diskpart detects disk as Disk 1 as (almost) 3TB drive.

So how can i achive splitting the 3TB drive into two 1.5Tb disks?

  • This will be related to the NTFS 2TB issue - notably the cluster size in your situation - it'll probably be 512. You can change your NTFS cluster size in the partition format utility... set it to 4k and you should be able to create an NTFS partition that fills your disk... – Kinnectus Jul 16 '15 at 14:47
  • Unfortunately no. Even if i change cluster size to 4k it still offers only 1.99TB. – Pastx Jul 16 '15 at 15:01
  • You need to delete the RAW partition as you've only created a 2TB partition and trying to format it - so it's only ever going to be 2TB. Delete the RAW partition and you should be able to create a new partition but make sure you select the right cluster size otherwise it'll create another 2TB partition. – Kinnectus Jul 16 '15 at 15:04
  • 1
    Relevant: My 3TB HD can't use 3TB? (only 2) – DavidPostill Jul 16 '15 at 15:05

The error says it all, did you read it? The conversion to GPT didn't succeed so you can't create a partition beyond 2TB. You can also see that the Gpt column for the corresponding disk isn't highlighted after the convert command

diskpart output

The reason is that diskpart in Windows has very limited functionality and can't convert some disk types to others on-the-fly. It needs you to remove all partition first before converting to GPT

To change a master boot record disk into a GUID partition table disk using the Windows interface

  1. Back up or move the data on the basic master boot record (MBR) disk you want to convert into a GUID partition table (GPT) disk.
  2. If the disk contains any partitions or volumes, right-click any volumes on the disk and then click Delete Partition or Delete Volume.
  3. Right-click the MBR disk that you want to change into a GPT disk, and then click Convert to GPT Disk.

To change a master boot record disk into a GUID partition table disk using a command line

  1. Back up or move the data on the basic master boot record (MBR) disk you want to convert into a GUID partition table (GPT) disk.
  2. Open an elevated command prompt (right-click Command Prompt, and then click Run as Administrator) and type diskpart. If the disk does not contain any partitions or volumes, skip to step 6.
  3. At the DISKPART prompt, type list disk. Make note of the disk number you want to convert.
  4. At the DISKPART prompt, type select disk <disknumber>.
  5. At the DISKPART prompt, type clean.
  6. At the DISKPART prompt, type convert gpt.


To convert a disk to GPT without losing data you need 3rd party solutions like gdisk, MiniTool Partition Wizard, AOMEI Partition Assistant, EaseUS Partition Master... (I'm not affiliated with any of them)

Windows 10 version 1703 and up also have a built-in ability to do a lossless conversion called MBR2GPT.EXE

That said, it's possible to create a 3TB MBR disk with two 1.5TB partitions because as long as the last partition begins before the 2TB mark and doesn't last longer than 2TB then it'll be fine. Of course you need OS support for this, and also need a 3rd party disk partitioner instead of diskmgmt.msc

Since partitioning information is stored in the MBR partition table using a beginning block address and a length, it may in theory be possible to define partitions in such a way that the allocated space for a disk with 512-byte sectors gives a total size approaching 4 TiB, if all but one partition are located below the 2 TiB limit and the last one is assigned as starting at or close to block 232−1 and specify the size as up to 232−1, thereby defining a partition that requires 33 rather than 32 bits for the sector address to be accessed. However, in practice, only certain LBA-48-enabled operating systems, including GNU/Linux, FreeBSD and Windows 7[20] that use 64-bit sector addresses internally actually support this


However GPT would be a safer solution


Windows cannot convert disk format without deleting all partition, so it returns an error in cmd

The problem is due to the disk format. The maximum capacity for MBR disk is 2TB.


  1. delete that 2TB partition
  2. right click on "disk 1"
  3. select "convert to GPT"
  4. you should be able to create two 1.5TB partitions.

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