How to add Unallocated space in Windows Server 2016

by John, Updated on: August 12, 2020

This article introduces how to add Unallocated space to C drive in Windows Server 2016, move and add Unallocated space to system partition without losing data.

Unallocated space is a writable area that does not belong to any partitions. Before writing files to this area, you must create new partition and format it with a file system. Besides creating new partition, Unallocated space can be added to other existing partition to increase free space. It is helpful especially when system C: drive is getting full. By adding Unallocated space to C drive, you can fix this issue without wasting a long time to back up, recreate partitions and restore everything. In this article, I'll introduce how to add Unallocated space in Windows Server 2016 with native Disk Management and partition editor software.

1. Add Unallocated space to partition with Server 2016 Disk Management

Windows Server 2016 has built-in Shrink and Extend Volume functions in Disk Management console. Shrink Volume is used to decrease partition and make Unallocated space, Extend Volume is used to increase partition by merging Unallocated space. However, many people encountered problem while adding Unallocated space in Windows 2016 server. The typical example is that they cannot add Unallocated space to C drive after shrinking D or other partitions.

As you see in the screenshot, Extend Volume greyed out for both C: and E: drive after shrinking D.

Cannot extend volume

Why cannot add Unallocated space to C drive in Server 2016 Disk Management:

  1. Extend Volume can only merge Unallocated space to the left contiguous partition.
  2. Shrink Volume can only make Unallocated space on the right while shrinking partition.

Unallocated space that shrunk from D drive is non-adjacent to C, E is on the right side, therefore, Server 2016 Disk Management cannot add Unallocated space to C or E drive.

Additional shortages of Disk Management to combine Unallocated space:

  1. Both Shrink and Extend Volume functions only support NTFS partition. So, to FAT32 and other partitions, Disk Management cannot add Unallocated space to partition.
  2. On MBR disk, if the contiguous partition D is Logical, you still cannot extend C drive after deleting D.

In short: with Disk Management tool, you cannot extend E: drive with the left contiguous Unallocated space. To extend C drive, you must delete D: to get right contiguous Unallocated space. 3rd-party software can move partition D towards right, then Unallocated space will be next to C drive, so they can add non-adjacent Unallocated space to C drive in Windows 2016 server.

2. How to add Unallocated space to C drive in Windows Server 2016

There are many software that is able to move and add Unallocated space to C drive in Windows Server 2016, however, you'd better back up first and run the safest tool. Otherwise, there's potential data loss risk. Better than other tools, NIUBI Partition Editor has powerful technologies to protect system and data, for example:

While moving Unallocated space behind C drive, all files in drive D will be moved to new locations, too. The more files in it, the longer time to move. Because of the advanced file-moving algorithm, NIUBI is 30% to 300% faster. It is helpful especially when this operation requires server rebooting.

How to move and add Unallocated space to C drive in Windows Server 2016:

  1. Download NIUBI Partition Editor, right click drive D and select "Resize/Move Volume", drag the middle towards right in the pop-up window. Then Unallocated space will be moved next to C drive.
  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. (Disk partitions won't be modified until click Apply to confirm.)

The pending operations marked as Check can be done in Windows, the ones marked with refresh symbol requires server rebooting.

Watch the video how to operate:

Video guide

The steps are the same no matter you use physical server with SSD, HDD, any types of hardware RAID, or virtual server in VMware/Hyper-V.

3. Move/Add Unallocated space to C drive from another separate disk

In few servers, there's no other partitions or not enough free space on the same disk, many people are wondering whether it is possible to move Unallocated space to C drive from another disk. The answer is no.

No software can transfer space between 2 separate disks. When there's no available free space in a disk, there are 2 options:

  1. If you use physical server, follow the steps to copy disk to a larger one and expand partition(s) with additional disk space.
  2. If you run virtual server, follow the steps to increase size of the virtual disk in VMware or Hyper-V. After that, additional space will be shown as Unallocated at the end of disk, then follow the steps in the video above to move and add Unallocated space to C drive (or other partitions).

In Summary

To move and add Unallocated space to C drive in Windows 2016 server, the native Disk Management is useless in most cases. To accomplish this task, you'd better back up and run safe partitioning software. Besides shrinking, moving and extending partition, NIUBI Partition Editor helps copy, convert, defrag, wipe, hide partition, scan bad sectors and much more.

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