Solution - Can't Extend C Drive in Windows Server 2019/2022

by Allen, Updated on: July 30, 2022

When C drive is running out of space, many people want to extend C drive rather than recreating partitions and restoring from backup. There's "Extend Volume" function in native Disk Management tool. Some people try to increase C drive space but failed, because "Extend Volume" is grayed out. In this article, I'll explain why Disk Management is unable to extend C drive in Windows Server 2019/2022 and what to do when you can't extend C drive partition.

Why cannot extend C drive in Windows Server 2019/2022 Disk Management

Firstly, you should know that Disk Management can only shrink and extend  NTFS partition, FAT32 and other types of partitions are not supported. Because all system C: drive are formatted with NTFS file system by default, this is not an issue to system partition, .

No adjacent Unallocated space is the most common reason why you can't extend C drive in Server 2019/2022 with Disk Management.

The size of a physical disk is fixed. You can resize a partition, but you cannot decrease a 512GB disk to 256GB or increase it to 1TB. Therefore, before extending C drive, there must be "Unallocated" space on the same disk. To get such space, you may either shrink or delete a partition on this disk. You won't lose files (in most cases) when shrinking partition with Disk Management. The problem is that Disk Management cannot extend this Unallocated space to other partition.

Extend Volume disabled

Because "Shrink Volume" function in Disk Management can only make Unallocated space on the right. With "Extend Volume" function in Disk Management, Unallocated space can only be extended to the left contiguous partition.

As you see in the screenshot, I got 20GB Unallocated space after shrinking D drive in my server. C drive is nonadjacent and E is on the right of this Unallocated space. Hence, Extend Volume  greyed out to both partitions.

If your system disk is MBR, there's another reason why you cannot extend C drive in Windows Server 2019/2022 with Disk Management.

Extend Volume disabled

Because it doesn't work to shrink D and extend C drive.  Some people are wondering whether it's possible to enable Extend Volume by deleting D. The answer is yes on  GPT disk, but to MBR disk, it depends.

On MBR disk, the partitions that you want to delete and extend must be the same Primary or Logical. Because C drive is always Primary, if D is Logical, you still cannot extend C drive after deleting D in Disk Management.

After deleting a Logical drive, the space will be changed to "Free" instead of "Unallocated". To convert "Free" space to Unallocated, you must delete all Logical partitions and then delete the "Extended" partition.

In my server, if I want to extend C drive without any software, I must delete D and E drive. Obviously, this is not a good idea.

What to do when you are unable to extend C drive in Server 2019/2022

If you shrunk D (or E) drive and got nonadjacent Unallocated space, you need to move partition D to the right and make Unallocated space contiguous to C drive. In some servers, there's another Recovery,  EFI or OEM partition in the middle of C and D drive. In that case, you need to move these partitions to the right, too. The method to move these partitions are the same.

Steps when you can't extend C drive in Windows Server 2019/2022 after shrinking D:

  1. Download NIUBI Partition Editor, right click D: drive and select "Resize/Move Volume".
  2. In the pop-up window, drag the middle  of D drive 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 will be combined to C drive.
  4. Click Apply on top left to confirm and execute.

Video Server 2019

If you are unable to extend C drive in Server 2019/2022 after deleting Logical partition D, follow the steps below:

  1. Recreate partition with the "Free" space in Disk Management.
  2. Delete or shrink this new volume with NIUBI Partition Editor.
  3. Right click C drive and run "Resize/Move Volume" to add Unallocated space to C drive.

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 left or right 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 will be 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 will be made on the right.

Shrink towards left

This Unallocated space can be combined to either adjacent NTFS or FAT32 partition directly. It also can be moved to combined to nonadjacent partition on the same disk. Learn how to move and merge Unallocated space in Windows Server 2019.

Steps are the same no matter you use SSD, HDD, any types of hardware RAID or run the server in VMware/Hyper-V/Virtualbox.

Better than other tools, NIUBI Partition Editor has Virtual Mode, Cancel-at-well, 1-Second Rollback and Hot-Clone technology to protect your system and data. Besides shrinking, moving and extending partitions, it helps you do many other disk partition management operations.