How to Extend System Partition for Windows Server 2016

When you use Windows Server 2016, you may find that its partitions are not reasonable, especially the system partition would be too small. All system-relevant files are stored in a C drive, with your daily use, a C drive with insufficient capacity will affect your Server performance. Thus, you need to find a way to extend the system partition for Windows Server 2016.

Failed to extend system partition via Disk Management in Windows Server 2016

To extend the system partition, Windows Server 2016 Disk Management has a function called "Extend Volume" that you can use to extend the partition.  After you open "Disk Management",  right-click the system partition, and select "Extend Volume", then, you can extend the partition as you want. 

But, the problem is that not all users can successfully extend the system partition via Disk Management. Many people may meet the situation that the "Extend Volume" is grayed out. 

▶ Why is Windows Server 2016 Disk Management "Extend Volume" greyed out?

Although Windows Disk Management has the "Extend Volume" for you to extend system partition for Windows Server 2016,  its "Extend Volume" feature has 2 requirements:

1. There must have unallocated space on the target disk.
2. The unallocated space adjacent to the partition you want to extend, and must be on the right side of the partition.

Otherwise, the "Extend Volume would" be greyed out like the situation we mentioned above.

Extend system partition for Windows Server 2016 without losing data

If there is no unallocated space on the right side of the system partition, how could you extend the system partition for Windows Server 2016?

To use Disk Management to extend partitions without unallocated space, you need to delete the partition behind the target partition, in our case, that means your D drive, and that would take a risk of losing data on the deleted partition.

To extend the system partition without losing data for Windows Server 2016 effortlessly when the Extend Volume of Disk Management grayed out, you can use a third-party software AOMEI Partition Assistant Server, which provides you with 2 methods to extend the system partition for Windows Server 2016. Even if there is no unallocated space near the system partition, this tool can enlarge your crowded C drive.

For different situations, we provide 2 cases, you can choose a suitable method for your Server 2016.

▶ Method 1. Merge partition

There is unallocated space on the right side but not adjacent to the system partition as the following picture shows. The unallocated space is behind D: drive.

Step 1. Install and run AOMEI Partition Assistant. Right-click C: drive directly, choose “Advanced” and select “Merge Partition”.

Step 2. You can use this feature to merge C: drive with the adjacent partition or non-adjacent unallocated space on the disk or both. 

Step 3. Click "OK" to back to the main interface of this software. Click "Apply" on the toolbar to execute the operations.

▶ Method 2. Allocate free space

If there is no unallocated space on the disk, you can try to extend C: drive with the free space of other partitions.

Step 1. Install and run the partition manager for Windows Server. In the main interface, right-click the partition that has much free space (here is partition D) and choose “Allocate Free Space.”

Step 2. In the pop-up window, type the free space that you want to transfer to C drive from D and choose C drive as the destination location. Then, click “OK”.

Step 3. In the home interface, you can see that the C drive has been extended with the free space that is moved from the D drive. Click “Apply” and “Proceed” to commit the pending operations.

To sum up

Extending system partition for Windows Server 2016 with AOMEI Partition Assistant will avoid many unnecessary works in Disk Management. This tool supports Server 2025, and all Server 2025/2022/2019/2016/2012. Besides extending C drive size, you can also convert to GPT/MBR, clone disk/partition, move installed apps... to organize your devices as you need.