Cannot extend volume

Cannot extend volume in Windows Server 2016

This article talks about why you can’t extend partition in Windows Server 2016 with Disk Management built-in Extend Volume functionality, and what to do when you unable to extend volume.

Hard disk drives are allocated while installing Operating System, but you need to reallocate the partitions after running the server for a period of time. The typical example is lack of free space especially to system C drive.

To help solve this problem, Microsoft provides Extend Volume functionality in Disk Management snap-in from Server 2008. Windows Server 2016 inherited this functionality without improvement. Many server administrators feedback that they cannot extend volume in Disk Management, because Extend Volume is greyed out.

There are several reasons that cause you unable to extend volume in Server 2016 Disk Management, but to solve this problem, it is very easy.

Cannot extend volume

Why cannot extend volume in Server 2016 DM?

In fact, Extend Volume has many restrictions and only few partitions can be extended with this utility.

Reason 1 Limitation of MBR disk

MBR (Master Boot Record) hard disk has many limitations, one of which is the restriction between Primary and Logical partition. You cannot extend a Primary partition by shrinking or deleting a Logical partition, and vice versa. (more about the restriction)

Another common limitation is that it only supports maximum 2TB disk space. Microsoft begin to abandon MBR and format the hard disk as GPT by default when installing Server 2016. So, you are not likely to encounter this issue except that you upgrade from previous Windows.

Tips Windows Disk Management doesn’t show you whether you are using MBR or GPT disk, but you can identify from 2 points:

  1. If there are more than 4 Primary partitions in a disk, this disk must be GPT.
  2. If there is one or more Logical partition in a disk, this disk must be MBR.

Reason 2 No adjacent Unallocated space

This is the most common reason why you can’t extend volume in Server 2016 Disk Management. Many people shrank drive D and got some Unallocated space, but Extend Volume is disabled for C drive. From Microsoft explanation: Extend Volume only works when there is adjacent Unallocated space on the right side of the partition that you want to extend.

After shrinking drive D, Unallocated space can only be produced on the right side of D rather than C, so you cannot extend volume C drive.

Cannot extend volume

Reason 3 Not supported partition

In fact, both Shrink and Extend Volume functionalities support NTFS partition only, thus, another common FAT32 partition cannot be extended, even though there is adjacent Unallocated space on the right side.

Can't extend FAT32

What to do when can’t extend volume?

In this situations, you need server partition manager software such as NIUBI Partition Editor. Better than other tools, NIUBI is integrated 1 Second Rollback and virtual mode to protect system and data.

Solution 1 Move Unallocated space

When you cannot extend partition in Server 2016 Disk Management because the Unallocated space is nonadjacent, you just need 1 step to move the Unallocated space. For example, how to extend C drive with the Unallocated space behind D.

Download and NIUBI Partition Editor Server, similar with Disk Management, you’ll see all disk partitions on the right. Right click partition D and select “Resize/Move Volume”.

NIUBI Partition Editor

Drag the middle position rightwards in the pop-up window.

Move Unallocated

Click OK, Unallocated space is moved to the left side of D. Click “Apply” on top left to execute.

Tips NIUBI Partition Editor works in virtual mode and real disk partition won’t be modified until you click Apply to confirm. If you did something wrong, simply click “Undo” to cancel. The pending operations marked as Check can be done in desktop without rebooting.

Unallocated moved

Check in Disk Management after it complete. As you see, 20GB Unallocated space is moved to the other side and Extend Volume is enabled for C drive.

Extend Volume activated

To add the Unallocated space to C drive, you still just need 1 step to drag.

Right click C drive and select “Resize/Move Volume” again, drag the right border towards right side in the pop-up window.

Extend C drive

Click OK, Unallocated space is combined to C drive. (Remember to click Apply)

C drive extended

Solution 2 Merge adjacent Unallocated space

If you cannot extend a drive in Server 2016 Disk Management because it is FAT32, the same with above:

  • When there is adjacent Unallocated space on either side, simply drag the border towards the other side with “Resize/Move Volume” to merge the Unallocated space.
  • If the Unallocated space is nonadjacent, drag the middle position to move the Unallocated space, and then combine to the drive that you want to extend.

If you still do no understand how to operate, watch the video:

In Summary

Windows native Disk Management cannot produce Unallocated space on the left side when shrinking a volume, it can’t move partition or the Unallocated space, so you can’t extend another partition with Extend Volume. In this situation, run NIUBI Partition Editor to move the Unallocated space to adjacent (on either side) and then combine to the drive that you want to expand. Both NTFS and FAT32 partitions are supported.


1 step to fix cannot extend volume partition in Windows Server 2016.
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