By Cherry / Last Updated August 8, 2019

When to change partition size in Windows Server 2012?

Changing partition size does not only mean increasing partition size, but also mean reducing partition size. In different situations, you need to make different operation (increase or decrease partition size) in Windows Server 2012.

When one of your hard drives (especially the system C drive) is too small or filled with all types of applications, the "low disk space" warning will keep popping out at the right down corner. As a result, the Windows Server 2012 may run slower and slower; some applications can be even frozen, then what you can do the best is to extend the partition size instead of cleaning up hard drive.

However, when some partitions on your disk are too bigger and only a little space has been used (lots of space are unused), you might be eager to reduce the partition size to make them smaller and create a new partition on the unoccupied space for other purposes.

How to adjust partition size in Windows Server 2012?

When it comes to changing partition size on Server 2012, there are 2 options: Windows built-in Disk Management and third party partition software.

Option 1. Change partition size with Disk Management

Disk Management is a Windows native tool on Windows Server 2012 and other operating systems. It has the “Extend Volume” and “Shrink Volume” features for Windows Server 2012 users to change partition size. With those two functions, you can shrink and extend a partition in few steps.

  • To reduce partition size

Step 1. Press Windows+R on your keyboard to open Run dialogue, input “diskmgmt.msc” and press Enter to open Disk Management window.

Step 2. Right click the partition you want to decrease and select “Shrink Volume”.

Shrink Volume Dm

Step 3. Enter the amount of space (1024MB=1GB) and click “Shrink” to execute the operation.

Shrink Size

In a while, this selected drive will be shrunk to the desired size.

  • To increase partition size

Step 1. Right click the NTFS partition that has right adjacent unallocated space and select “Extend Volume”.

Extend C Drive

Step 2. Click “Next” in the pop-up Extend Volume Wizard window.

Step 3. Click “Next” to select disk and space, or keep the defaults.

Step 4. Click “Finish” to execute.


Restrictions of Disk Management

Although Disk Management can be helpful when you are changing partition size on Server 2012, it has the following limitations on extending or shrinking partition size.

  • Only NTFS partition can be shrunk and extended. FAT32 and other types of partition are not supported.

  • Unallocated space can only be generated on the right side of the partition you just shrank.

  • To extend a volume, there must be adjacent unallocated space on its right side. Otherwise, you may have to delete the partition behind the to-be-extended partition.

  • In a few cases, you can only shrink little space because there are some unmovable files on the partition, even if there is large amount of free space in the volume.

Option 2. Change partition size with partition manager

From above, we know that Disk Management is not versatile enough when it comes to resizing partitions in Windows Server 2012. So you might want to use a much more powerful partition manager like AOMEI Partition Assistant Server. It can resize partition on Windows Server 2012 (R2) more flexibly with the following advantages:

  • Supports resizing (increasing or reducing) NTFS and FAT32 partition size in Windows Server 2012.

  • Supports moving partition which locates between the partition you want to extend and the unallocated free space. Then the unallocated space can be adjacent behind the partition which needs to be extended.

  • Enables you to directly merge unallocated space into a partition no matter where it is on the same disk.

What’s more, AOMEI Partition Assistant Server is compatible with Windows Server 2003, 2008 (R2), 2016, 2019 Windows SBS and all Windows PC OSes, not only just Windows Server 2012.

To increase partition size, there must be an unallocated space on the same disk as the partition you plan to extend. If there's not, you could shrink other partition to generate one. Below is how to shrink one partition and then extend another partition.

Step 1. Install and launch AOMEI Partition Server. You will see the main interface containing with the basic situation of your hard drive(s). To extend C: drive in Windows Server 2012 R2, here you should shrink D: drive first. Right click D: drive, select “Resize Partition”.

Resize A Partition

Step 2. You can drag D partition towards to left side to release an unallocated space. At the same time, you can move this partition to the right side to make the generated unallocated space near to C partition.

Move And Resize Partition

Step 3. Then you will back to the main interface and you can see there is an unallocated space behind C: drive. Here, right click C: drive, select “Resize Partition”.

Resize Destination Partition

Step 4. Here you can drag the slide bar to the right edge to extend C: drive. Click "OK".

Extend Partition Size

Step 5. Finally, you can see the C: drive has been extended in the main interface. Click “Apply” and “Proceed” to commit the pending operation.


Thus, you have finished extending C: drive in Windows Server 2012 R2. If there have been an unallocated space on the disk but not behind the C drive, you can use “Merge Partition” of AOMEI Partition Assistant Server.

Right click the C partition and select “Merge Partition” from the drop-down menu. In the next window, tick the unallocated space and click “OK”. Finally, click “Apply” and “Proceed”.

Choose Unallocated Space


AOMEI Partition Assistant Server permits you to change partition size in Windows Server 2012 (R2) more easily than Disk Management. It has many other features like create, format, delete, wipe, move, check partitions, wipe hard drive, etc. Besides, this software contains “Allocate Free Space” function to satisfy you more requirements of resizing partition on Windows Server computer, which can assign free space from one partition to another partition directly.

Besides change partition size on Windows Server 2012 (R2), it can do more for Windows Server, such as migrating OS to SSD or HDD, converting disk between MBR and GPT partition styles, making WinPE bootable CD/USB, etc.

If you want to use AOMEI Partition Assistant on unlimited PCs and servers within your company, please choose Unlimited Edition; if you want to make a profit by providing technical services to your clients, please choose Technician Edition.