Cannot Extend C: Drive in Windows Server 2016 (Reason & Solution)

by Jacob, Updated on: September 24, 2021

After running a server for a period of time, you may want to shrink a large partition to create more, or expand a partition that is getting full. To help resize partition without losing data, Microsoft added Shrink Volume and Extend Volume functions in Disk Management from Server 2008, but both functions have many restrictions. Windows Server 2016 inherited the same functions without improvement, so many people feedback that Disk Management can't extend C drive in Windows 2016 server after shrinking or even deleting D drive. In this article, I'll explain why you are unable to extend C drive in Server 2016 Disk Management and how to solve this problem easily.

Why cannot extend C drive in Server 2016 Disk Management?

Reason 1: No adjacent Unallocated space

This is the most common reason why you cannot extend C drive in Windows 2016 server. A 160GB physical disk can't be increased to 250GB, so before extending a volume, you must delete or shrink other volume to get Unallocated space. If there's no or you did not make such space, of course you cannot extend C: drive in Windows Server 2016.

Extend Volume disabled

If you delete a volume, all files in it will be deleted, too. Therefore, many people tried to shrink the adjacent partition D (or E:). The problem is, Extend Volume still greyed out.

Extend Volume greyed out

When you shrink D drive, Disk Management only gives you an option to enter an amount, then Unallocated space is made on the right side of D. But to extend C drive with Disk Management, Unallocated space must be behind C drive (on the left side of D). In this situation, you need to move partition D towards right.

Reason 2: Restriction between Primary and Logical partition

This issue only exists on MBR style disk. Most of system partition are Primary, if the right contiguous partition D is Logical, you still cannot extend C drive in Server 2016 Disk Management even if you can delete D.

Cannot extend

As you see in the screenshot, Extend Volume is disabled for C: drive after deleting the right contiguous partition D.

This is because:

In GPT disk, all partitions are Primary, but in MBR disk you can only create maximum 4 Primary partitions or 3 Primary plus an Extended partition. Unlike Primary partition that works as independent unit, Logical drives are part of the Extended partition. After deleting a Logical drive, you'll get Free space instead of Unallocated space.

On MBR style hard disk, Free space that deleted from a Logical drive can't be extended to any Primary partition. Unallocated space that deleted from a Primary partition can't be extended to any Logical drives.

Reason 3: 2TB restriction on MBR disk

In few servers, the system is almost full, some server administrator replace it with a large disk. If there's adjacent Unallocated space on the right of C drive, but you still cannot extend C drive in Windows Server 2016 Disk Management, check the size of C drive and the whole disk. On MBR disk, only 2TB disk space can be used. If your C drive is already 2TB, you must convert this disk to GPT in advance.

What to do if unable to extend C drive in Windows Sever 2016?

Open your own Disk Management and find out the reason, follow the corresponding method below according to your own disk partition configuration.

Method 1: move partition and Unallocated space

If you've shrunk D (or E) drive and got nonadjacent Unallocated space, you need to move D (or E) drive towards right and make Unallocated space next to C drive.

How to fix the issue if unable to extend C drive in Server 2016 Disk Management:

  1. Download NIUBI Partition Editor, right click D (or E) drive and select "Resize/Move Volume", put the mouse pointer in the middle and drag towards right in the pop-up window.
  2. Right click C: drive and select "Resize/Move Volume" again, drag right border towards right to combine Unallocated space.
  3. Click Apply on top left to execute.

NIUBI Partition Editor is designed to work in its virtual mode first, 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 without rebooting server.

Watch the video how to operate:

Video guide

Method 2: shrink partition with NIUBI

What to do if you cannot extend C drive in Windows Server 2016 Disk Management after deleting Logical D drive:

  1. Right click the Free space in Disk Management and select "New Simple Volume".
  2. Right click the new volume in NIUBI Partition Editor and select "Resize/Move Volume" option. Drag the left border towards right in the pop-up window to shrink it.
  3. Right click C drive and select "Resize/Move Volume" option again, drag the right border towards right to combine this Unallocated space.

Remember to click Apply to take effect.

Method 3: convert MBR to GPT

Few people use 2TB+ disk as system disk. If you did this, to extend C drive and use full disk space, follow the steps to convert MBR disk to GPT. You can accomplish this task without any software, but firstly you should find out if your disk partition configuration meet the requirements.

Be cautions while extending system partition C

Unlike data read-only program, partitioning software will modify parameters of associated disk, partition and files, so there's potential system/data damage risk, it is important to back up in advance and run safe disk partition software.

Better than other tools, NIUBI Partition Editor has innovative technologies to protect your system and data such as:

In addition, it is 30% to 300% faster because of the advanced file-moving algorithm, it's very useful when you shrink and move partition with large amount of files.

In Summary

Because of many limitations, Disk Management tool cannot extend C drive in Windows 2016 server by shrinking or even deleting other volume. With NIUBI Partition Editor Server, you can solve this problem fast and easily. Beside shrinking, moving and extending partition, it helps merge, copy, convert, hide, wipe partition, scan bad sectors and much more.

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