Shrink C Drive (System Partition) in Windows Server 2016

by Jordan, Updated on: March 6, 2022

Sometimes you need to shrink C drive in Windows Server 2016, for example: you forgot to edit disk and create more partitions when installing Operating System, so all available disk space are occupied by C: drive. As we know, it is a bad idea to put everything into system partition. Then what to do, start from scratch? No, you can shrink partition C in Server 2016 with native Disk Management without losing data, then part of the free space in C drive will be converted to Unallocated space. After that you can create new volume or add this space to other partition.

However, because of some restrictions of Disk Management, sometimes it cannot shrink C drive. This article introduces how to shrink system C drive in Windows Server 2016 with Disk Management, what to do when it doesn't work, and how to extend other partition after shrinking C drive.

Shrink C drive partition in Server 2016 with Disk Management

From Windows Server 2008, Microsoft added "Shrink Volume" function in native Disk Management utility, which is able to decrease partition size without losing data and on the fly. It is fast and easy to use.

How to shrink C: drive in Windows Server 2016 with native Disk Management:

  1. Press Windows and X together on the keyboard and select Disk Management in the list.
  2. Right click C drive and select Shrink Volume.
    Shrink C drive
  3. Waiting for Disk Management to query available free space, then simply click Shrink to decrease with default maximum available space, or enter a smaller amount by yourself.
    Enter amount

In a short time, system C partition is shrunk to 39.45GB in my server, 120GB free space is now converted to Unallocated behind it.

C drive shrank

It is easy to shrink partition in Server 2016 Disk Management, but as I said above, you can't shrink C drive in some situations.

Why cannot shrink C drive in Windows Server 2016

In fact, Shrink Volume only supports NTFS partition, when you shrink a FAT32 partition, Shrink Volume is greyed out. However, most of system partitions are formatted with NTFS by default, so it is not an issue while shrinking system C drive.

When shrinking partition C in Windows Server 2016, there are 2 common issue.

1. Not enough space

Cannot shrink C

When I click Shrink, I received the error message - "There is not enough space available on the disk(s) to complete this operation."

Error message

Disk Management gives maximum available space in the shrinking window by default. Before clicking Shrink button, if any Windows Update or other files saved into C drive, the available free space is less than calculated. If you also receive this error, simply run Shrink Volume again.

2. File System error

Sometimes, when there's File System error in a partition, Disk Management won't allow shrinking it. As you see in the screenshot, there's 7.53GB free space in system C drive, but in the shrinking window, available free space is shown as 0.

Cannot shrink

3. Unmovable files

If there are large amount of free space in C drive but Disk Management gives you little space to shrink, it means that there are some "unmovable" files located in this partition. This is another common issue while shrinking system C drive in Windows Server 2016.

Tip of shrinking

In the Shrink window, there is a tip "You cannot shrink a volume beyond the point where any unmovable files are located."

For example: there are 4 blocks in C drive. If the unmovable files are located in block 3, you cannot shrink volume C to block 2 even though it is blank.

Unmovable files

In this case, you need to run NIUBI Partition Editor Server, which is able to move these unmovable files, so you can shrink C drive to minimum size if you want.

Why cannot extend D or E after shrinking C drive

After shrinking C drive to get Unallocated space, you can easily create new partitions. But if you want to extend system reserved partition, D drive or any other partitions, Disk Management cannot help you.

Cannot extend

As you see in the screenshot, after shrinking C drive, Extend Volume is greyed out for all other partitions.

This is because: "Extend Volume" function can only add Unallocated space to the contiguous NTFS partition on the left, but Shrink Volume function can only make Unallocated space on the right.

To solve this problem, you need to run NIUBI Partition Editor to combine Unallocated space to other partition(s).

Better way to shrink C drive volume in Windows 2016 server

Comparing with Windows Disk Management, NIUIBI Partition Editor has more advantages such as:

How to shrink C drive (system partition) in Windows Server 2016 with NIUBI:

  1. Download NIUBI Partition Editor, right click C drive and select "Resize/Move Volume".
  2. In the pop-up window, drag either border towards the other side. If you drag right border towards left, Unallocated space is made on the right side of C drive.
  3. Click Apply on top left to execute. (NIUBI is designed to work in its virtual mode, real disk partitions won't be changed until click Apply to confirm.)

Watch the video how to extend other partition by shrinking system C: drive in Windows Server 2016:

Video guide

In Summary

Windows Server 2016 provides native Shrink Volume function in Disk Management, but it is not the best tool because of many restrictions. It can only help you shrink NTFS partition to create new volume. In addition, sometimes it cannot shrink system C drive. Even if it shrunk C drive successfully, it cannot expand other volumes.

If you encountered any issue while shrinking C drive with Disk Management or if you want to expand other volume by shrinking partition C for Windows 2016 server, run NIUBI Partition Editor. Better than other tools, it has innovative 1 Second Rollback, Virtual Mode and Cancel-at-well technologies to protect system and data. In addition, it is 30% to 300% faster because of its advanced files-moving algorithm.