Cannot extend system C: drive in Windows Server 2016

Updated on: November 16, 2019

This article explains why cannot extend C drive in Windows Server 2016 Disk Management and what to do if you are unable to extend system C drive.

Windows Server 2016 provides Extend Volume function in native Disk Management, which is able to increase size of allocated partition without losing data. However, many people feedback that they can't extend C drive in Server 2016 Disk Management after shrinking D drive. This article explains all probable reasons why unable to extend C drive in Windows Server 2016 and the corresponding solutions.

Why cannot extend C drive in Windows Server 2016 DM?

Reason 1. No adjacent Unallocated space

This is the most common reason why you cannot extend partition C in Windows 2016 server.

A 160GB physical disk can't be increased to 250GB, so before extending a volume, there must be Unallocated space. If you did not delete or shrink other volume to get such space, of course you cannot expand C: drive.

Extend Volume disabled

By deleting a volume, all files in it will be deleted, too. In addition, in many servers, programs and some Windows services are installed in drive D, so this partition can't be deleted. Shrink Volume function can decrease partition and make Unallocated space without losing data, but this space can't be added to other partitions with Extend Volume function.

Extend Volume greyed out

When you shrink drive D, Disk Management only gives you an option to enter an amount, then Unallocated space is generated on the right side of D. But to extend C drive with Extend Volume, Unallocated space must be behind C drive (on the left side of D). In this case, 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 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 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, this is the reason why it is shown as Free after deleting.

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

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

Solution 1: If you cannot extend system C drive in Windows Server 2016 Disk Management after shrinking D, follow the steps below.

  1. Download NIUBI Partition Editor, right click drive D and select "Resize/Move Volume", drag the middle 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, 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

If the right contiguous partition D is FAT32 or Logical drive, Windows Disk Management is useless. But to NIUBI Partition Editor, there's no difference if you use NTFS or FAT32, Primary or Logical partition. If you've deleted other volume, simply add Unallocated space to C drive. If you have not, simply shrink other volume with NIUBI. Better than Disk Management, NIUBI can make Unallocated space on either side while shrinking.

Solution 2: If you cannot extend C drive in Windows Server 2016 because the data volume is FAT32 or Logical, follow the steps in the video:

Video guide

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 first and run safe disk partition software.

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

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

In Summary

Because of many limitations, Disk Management tool cannot help you extend C drive in Windows Server 2016 by shrinking D or other volume. It only works by deleting the right contiguous partition, in addition, this partition must be Primary.

With NIUBI Partition Editor Server, you can solve this problem safely and easily. It also helps merge, copy, convert, hide, wipe partition, scan bad sectors and much more.