Cannot extend volume in Windows Server 2012

Updated on: June 8, 2019

This article introduces why cannot extend volume with Diskpart command or in Windows Server 2012 R2 Disk Management, and what to do when unable to extend disk partition.

Why cannot extend partition via Server 2012 Diskpart

Many server administrators like to use command line tool. To extend partition in Windows Server 2012, Diskpart is one of the options, which is built-in tool integrated from Windows XP. However, it only works in special way. Many people receive error while extending partition with this native tool such as:

Press Windows and R, type diskpart and press Enter, type help extend and you'll see the reasons why Diskpart cannot extend volume.

Diskpart restrictions

To be short:

In other words, Diskpart can only extend NTFS by deleting the adjacent partition on the right.

Diskpart command prompt window only show you single partitions with associated information, it doesn't show disk structure or any Unallocated space.

Why can't extend volume in Server 2012 Disk Management

The same with Diskpart, Disk Management can't extend a partition by shrinking other one.

Unallocated space can only be made on the right while shrinking a partition (such as D:) with either native tool.

Neither Diskpart Extend command nor Disk Management Extend Volume function can merge the Unallocated space to nonadjacent drive C or the right partition E.

As the screenshot shows, Disk Management cannot expand partition C and E after shrinking D.

Extend volume disabled

There is an additional reason why Server 2012 Disk Management cannot extend partition.

Cannot extend

This issue only exists on MBR disk.

In MBR disk, there are maximum 4 entries in master boot record sector, so you can create maximum 4 Primary partitions, or 3 Primary plus an Extended partition. If you want to create more partitions, they must be created as Logical inside of the Extended partition.

If D is Logical partition, you still cannot expand C drive even by deleting it.

As you see in the screenshot, disk space of drive D is shown as Free after deleting. This Free space is still part of the Extended partition.

In this situation, you can extend C: drive via Diskpart without any software.

What to do when unable to extend disk partition

If you cannot extend volume C because the Unallocated space is non-adjacent, you can move Unallocated space to the left and then combine to C drive.

Steps to fix cannot extend partition in Windows Server 2012:

Step 1: Download NIUBI Partition Editor, right click the contiguous partition (D:) and select "Resize/Move Volume", drag middle position towards right in the pop-up window:

Move rightwards

Then Unallocated space is moved to the left side.

Move Unallocated space

Step 2: Right click drive C: and select "Resize/Move Volume" again, drag right border towards right in the pop-up window.

Expand C drive

Then Unallocated space is merged into C: drive.

Unallocated add to C

Step 3: Click Apply on top left to take effect.

If you want to merge Unallocated space to the right partition (E:) or extend any FAT32 partition, simply drag the border to combine (similar with STEP 2).

Watch the video how to fix Extend Volume disabled issue in Windows Server 2012:

Video guide

Besides shrinking, moving and extending partition, NIUBI Partition Editor helps merge, copy, convert, defrag, wipe, hide, scan partition and much more.