Shrink C drive

Shrink system C drive on Windows Server 2012

This article introduces how to shrink C: drive on Windows Server 2012 R2, shrink system partition with Disk Management and disk partition software.

Disk partitions have been allocated after installing Operating System, but sometimes you need to reallocate partitions. For example: you forgot to edit disk while installing OS, so the system partition C occupied all disk space. Another typical example is that drive D runs out of space but there is plenty of free space in C drive.

Shrink C drive

In these situations, you can decrease the system partition to create new or expand other volumes without reinstalling OS. To shrink system C drive on Windows Server 2012, there are two choices: native Disk Management and 3rd party disk partition software. Disk Management can shrink volume on the fly, but sometimes it cannot shrink system volume.

Shrink system partition without software

Windows Server 2012 has Shrink Volume feature in the built-in Disk Management utility, which is able to shrink system partition and any data volumes. It is easy, fast and able to decrease partition without rebooting server, but meanwhile, it has some restrictions.

Steps to shrink C drive with Server 2012 Disk Management:

  1. Press Windows and R key on your keyboard to start Run, type diskmgmt.msc and press Enter to open Disk Management.
  2. Right click C drive and select Shrink Volume.
  3. Enter the amount of space and click Shrink to proceed.

In a short time, the system C drive will be shrank. However, there is an issue shrinking volume with Disk Management: it can only shrink towards left and produce Unallocated space on the right side.

Shrink Volume

If you want to extend system reserved partition or data volume D with another Extend Volume feature, it is impossible. Extend Volume can only expand the drive with adjacent Unallocated space on its right side. As you see, 20GB Unallocated space is nonadjacent to the System Reserved partition and on the left side of drive D, so if you right click either partition, Extend Volume is grayed out.

Besides this limitation, Windows Server 2012 can’t shrink C drive in some special situations.

Cannot/unable to shrink C drive

There are 2 common reasons why Server 2012 Disk Management won’t let you shrink system C drive, I’ll show you one by one.

Reason 1 Conflicting available space

In the shrink volume window, you may either use the default value or enter an amount manually.

Enter amount

If you use the default maximum amount and simply click Shrink to start, you may encounter the error: “There is not enough space available on the disk(s) to complete this operation”.

Shrink error

As we know, many types of files are writing into C drive continuously, especially when Windows is downloading Updates, the available space is less than the maximum value. Thus, you cannot shrink C drive with the default value. To solve this problem, simply enter a smaller amount manually before clicking Shrink.

Reason 2 There are unmovable files

Have you noticed the tip in the same Shrink Volume window “You cannot shrink a volume beyond the point where any unmovable files are located.“? Comparing with other data volumes, system C drive has more such unmovable files, for example: Paging File, Hibernation and other large files. In this situation, Server 2012 Disk Management can’t shrink C drive, or allow you shrinking little space.

Shrink Volume tip

To solve this problem, you need 3rd party software such as NIUBI Partition Editor, which can move these “unmovable” files, so you can shrink C drive to minimum size with it if you want.

Shrink C drive and expand D

If you want to shrink C drive to expand D or other partitions, Server 2012 Disk Management cannot help you (as I explained above and highlighted with yellow). Then how to shrink system partition on Windows Server 2012 with disk partition software? You just need to drag and drop on the disk map and the Unallocated space can be generated on either side.

Steps to shrink C drive on Server 2012 (R2) with NIUBI:

Download NIUBI Partition Editor, right click C drive and select “Resize/Move Volume”.

Resize Volume

In the pop-up window, if you drag the left border rightwards:

Shrink C rightwards

Unallocated space will be generated on the left side:

Shrink C rightwards

In the pop-up window, if you drag the right border leftwards:

Shrink C leftwards

Unallocated space will be generated on the right side:

Shrink C leftwards

Watch the video how to shrink C drive to expand D and other partitions on Windows Server 2012:

In Summary

Windows Server 2012 native Disk Management can help you shrink system partition and data volumes, but in some situations it cannot shrink C drive. Furthermore, it only shrink a volume towards left and generate Unallocated space on the right side. Because of the limitation of Extend Volume, it cannot merge Unallocated space to any other partitions. To shrink and extend volume on Windows Server 2012, NIUBI Partition Editor is better choice.


How to shrink system C drive on Windows Server 2012 R2?
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