Cannot/Unable to Extend C Drive in Windows Server 2019

by Allen, Updated on: March 25, 2020

This article introduces why cannot extend C drive in Windows Server 2019 Disk Management and what to do if unable to extend system partition C in Server 2019.

After running the server for a period of time, you need to maintain disk drives, for example: create, delete, format, shrink and extend partition. To do this, Windows Server 2019 has its native Disk Management utility. C drive is very likely running out of space, because many types of files save into it continuously. In this situation, many people try to extend C drive with built-in Extend Volume function but failed, because Disk Management can't extend C drive after shrinking D or other partition. When right clicking C drive, Extend Volume is grayed out. In this article, I'll explain why you cannot extend C drive with Windows Server 2019 Disk Management and how to solve this problem with ease.

Why cannot extend C drive in Server 2019 Disk Management

Extend Volume only supports NTFS partition, FAT32 and other types of partitions cannot be extended. However, this is not an issue to system partition, because all system C: drive are formatted with NTFS file system by default.

The most common reason why unable to extend C drive partition in Windows Server 2019 is because that Unallocated space shrunk from D is nonadjacent to C.

As you see, I cannot expand C drive and E after shrinking D in my test server.

Extend Volume disabled

This is because:

Shrink Volume can only make Unallocated space on the right while shrinking partition D, but to expand C drive with Extend Volume, Unallocated space must be on the left side of D.

You have to move Unallocated space from right of D drive to the left, when the Unallocated space is next to C drive, Extend Volume is enabled.

In MBR disk, there's another reason why can't extend C drive in Server 2019 Disk Management. As you see in the screenshot, Extend Volume is still disabled for C drive after deleting D.

Extend Volume disabled

Cannot extend C drive by shrinking D in Disk Management, some people are wondering whether it's possible to enable Extend Volume by deleting D. The answer is yes to a GPT disk, but to MBR disk, it depends.

In MBR disk, the partitions that you want to delete and extend must be the same type. If one partition is Primary and the other one is Logical, Extend Volume will be disabled even after deleting the right contiguous partition.

In this situation, you need to run partition editor software.

What to do if unable to extend system C drive in Server 2019

  1. Download NIUBI Partition Editor, right click D: drive and select "Resize/Move Volume".
  2. In the pop-up window, drag the middle towards right, then Unallocated space will be moved to the left side.
  3. Right click C: drive and select "Resize/Move Volume" again, drag the right border towards right in the pop-up window, then Unallocated space is added into C drive.
  4. Click Apply on top left to confirm and execute.

Video Server 2019

To NIUBI Partition Editor, there's no difference to resize NTFS and FAT32 partition, or resize Primary and Logical partition. Unlike Disk Management, NIUBI can make Unallocated space on either side when shrinking a partition.

Right click a partition (such as D:) and select Resize/Move Volume, in the pop-up window you have 2 options.

Option 1: If you drag left border towards right or enter an amount in the box of Unallocated space before, then Unallocated space is made on the left.

Shrink towards right

Option 2: If you drag right border towards left or enter an amount in the box of Unallocated space after, then Unallocated space is made on the right.

Shrink towards left

You can shrink D to expand C drive directly, if you have shrunk D with Disk Management, or if you can only shrink E to get Unallocated space, follow the steps in the video above to move and add Unallocated space to C drive.

There's no difference if you use physical disk for local server, any types of hardware raid arrays or virtual machine in VMware/Hyper-V.

Take care of system and data while extending C drive partition

There are many software that has similar ability, but you'd better back up first and run safest tool, because there's potential system damage and data loss risk while moving and extending partitions. Better than other software, NIUBI Partition Editor is much safer and faster because of the advanced technologies:

Besides shrinking, moving and extending partitions, it helps you do many other disk/partition management operations.