How to Extend System/OS Partition in Windows Server 2019

by John, Updated on: July 30, 2022

After running Windows 2019 server for a period of time, OS partition C and system reserved partition is running out of space. In that case, you'd better try to fix this issue as fast as possible. Otherwise, server may stuck or reboot expectedly, there's no free space to install updates or receive error when upgrading Windows version. To solve this problem, nobody likes to waste a long time to start over or recreate partitions and restore from backup. It is much easier and faster to extend system partition for Windows 2019 server. In this article, I'll introduce how to extend system partition without software, how to extend OS and system reserved partition in Windows Server 2019 without losing data.

Extend Server 2019 system partition without any software

Windows Server 2019 has 2 native tools to help resize disk partition - Disk Management and diskpart. Disk Management has "Extend Volume Wizard" with graphical interface, diskpart works via command prompt. They works in different way, but they has same restrictions. No matter which tool you use to extend OS partition in Server 2019, your disk partition structure must meet the requirements:

  1. There's another partition (such as D) adjacent and on the right of C drive.
  2. You must delete this partition to get contiguous Unallocated space. (Caution: don't do this if you have programs or any Windows services in this partition.)

If there is no such partition or you cannot delete it, neither Disk Management nor diskpart can help you extend system drive. When extending C drive with Disk Management, the adjacent partition (D) must be Primary. Learn why Disk Management is unable to extend C drive by shrinking other partitions.

How to extend system partition in Windows Server 2019 via Disk Management:

  1. Right click Windows icon on bottom left and click Disk Management in the list.
  2. Right click the adjacent Primary partition D (E: in some servers) and select Delete Volume, then its disk space will be changed to "Unallocated".
  3. Right click system partition C: and select Extend Volume.
  4. Follow up the pop-up Extend Volume Wizard.

If you like to use command prompt tool, refer how to extend partition with diskpart in Windows Server 2019.

Better way to extend OS partition in Windows Server 2019

With disk partition software, you can shrink any partition on the same disk to get Unallocated space. When there's plenty of free space in adjacent D drive, you can shrink it and make Unallocated space on the left, then OS partition C can be extended easily. If you want to shrink nonadjacent partition, you can move Unallocated space on the left and then combine to C drive. 

Because there's potential system/partition damage risk while resizing partition in Windows server, you'd better make backup in advance and run safe partition software. Nobody likes to see server boot failure or partition corruption.

Better than other disk partition tools, NIUBI Partition Editor is much safer and faster because of the advanced technologies:

There are 2 methods to increase system partition size in Windows Server 2019. It depends on whether there's available free space on a didsk. Follow corresponding method according to your own disk partition configuration.

Method 1: extend system partition by shrinking other volume

In most of servers, there's at least one data volume with plenty of free space on the same system disk. You can shrink this partition to get Unallocated space and then add to system partition C.

Steps to extend OS partition C in Windows Server 2019 without data loss:

  1. Download NIUBI Partition Editor, right click the adjacent  D  drive and select "Resize/Move Volume". In the pop-up window, drag left border towards right or enter an amount in the box of "Unallocated space before". Then Unallocated space will be made on the left of this partition.
  2. Right click system partition  C and select "Resize/Move Volume" again, drag right border towards right to merge this Unallocated space.
  3. Click Apply on top left to execute, done.

Video Server 2019

If you want to increase C drive space by shrinking nonadjacent partition (such as E in my server), there's an additional step to move Unallocated space to the left before adding to C drive. If you use any types of hardware RAID array, do not break array or do any operation to RAID controller. Just follow the same steps above.

Method 2: extend system partition with another disk

If few servers, there's no other partition or not enough free space on the same disk. In that case, no software can extend system volume by moving free or Unallocated space from another separate disk. To solve this problem, you can copy system disk to a larger one and extend partition with extra disk space.

How to extend system partition in Server 2019 with a another disk:

Video Server 2019

If there's other partition and you don't want to clone disk, there's an another method to move partition. Move a partition from the system disk to another one, delete this partition and add its space to C drive.

How to extend system reserved partition in Server 2019

If you want to extend system reserved partition in Windows Server 2019, the steps are similar. You can shrink C drive and make Unallocated space on the left. Of course you can shrink other partition on the same disk, but it requires one more step to move Unallocated space. Watch the video how to increase system reserved partition in Windows Server 2019:

Video Server 2019

Extend system drive in VMware/Hyper-V virtual machine

If you want to extend system partition C in VMware/Hyper-V running Windows Server 2019, follow the steps in the first video when there's available free space on the same disk. If there's no available free space on a disk, expand virtual disk and then extend partition with extra space.

Besides shrinking, moving and extending partition in physical server and virtual machine, NIUBI Partition Editor helps you do many other disk partition operations.