Diskpart: Extend Server C Drive Step by Step

Here, you will learn how to use DiskPart to extend Server C drive step by step. An easy-to-use partition manager will also be shared to extend C drive in Server.


By Dervish / Updated on May 12, 2023

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The importance of extending C drive in Server

Usually, the C drive is the system partition either in PC or in server. If there are too much data in the system drive, the C drive will be running out of space quickly. As a result, your Server computer might run slower gradually and even frozen now and then. Besides, the “low disk space” warning will also pop out to interrupt your work. Then it is very important to extend Server C drive to optimize disk space usage. However, how to extend Server system partition? Please read the following content.

How to Extend Server C drive using diskpart

Diskpart is a Windows Server self-contained utility that deals with disks, partitions or volumes by running a command-line through scripts or direct inputting commands. To enlarge drive c, briefly, you only need to input "list volume", "select volume c" and "extend" into diskpart command interpreter. However, there are still some parts need your attention. Therefore, we list the specific steps in detail:

Step 1. Click Win+R and type "diskpart" in the Run box, then press Enter on the keyboard.

Step 2. Type "list volume" and press Enter on the keyboard to display the existing volumes on the computer.

Step 3. Type "select volume c" and press Enter on the keyboard to focus on volume c.

Step 4. Type "extend [size=n]" to extend volume c to disk n of size n.


Then, partition C will be extended with the unallocated space successfully.

①Contents in the square brackets are unnecessary. That is to say, you can only type "extend" to extend the size of the selected volume.
②"size=n " specifies the space, in megabytes (MB), to add to the current partition. If you do not specify a size, the disk is extended to use all the next contiguous unallocated space.
③In Server 2003, there is no "extend" or "shrink" command to help resize a partition.

Limitations of Diskpart to extend Server C drive

Although it seems quite simple to extend Server C drive with DiskPart Service, actually it has some limitations when extending (C) drive in Window Server operating systems.

✦ Only when there is adjacent unallocated space on the right side of the to-be-extended partition, extend command is valid.

✦ Only NTFS partition is supported to extend. Namely, the FAT32 or exFAT partition cannot be enlarged.

✦ Unallocated space is not displayed in the command window, so you don't know whether there is and where it is.

✦ Operations cannot be undone, the incorrect operation could cause data loss.

Alternative to DiskPart: extend Server C drive more flexibly

Because there are some restrictions to using DiskPart to extend C drive in Server, you might need an alternative to perform this task more flexibly and easily. AOMEI Partition Assistant Server is worth your trying. This partition manager is compatible with Server 2003, 2008 (R2), 2012 (R2), 2016, 2019, 2022, and SBS 2003, 2011.

As for extending Sever C drive, it breaks the limitations of DiskPart Service and extends C drive more flexibly. For example, when the unallocated space is not adjacent to C drive, it allows you to move the partition between the unallocated space and C partition to the right side, making them contiguous, and then extend C partition successfully. Or you can use the “Merge Partition” feature to directly add non-adjacent unallocated space into C drive, which requires fewer steps and time. Moreover, it is able to extend both FA32 and NTFS partitions.

Below are detailed steps to extend C drive by merging unallocated space into it:

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Step 1. You can download the Demo Version for a free trial. Launch AOMEI Partition Assistant Server. Right-click the C drive, choose “Advanced” and select “Merge Partitions”.

Merge Partitions

Step 2. Tick the unallocated space which is not right adjacent to C partition and click “OK”.

Choose Unallocated Space

Step 3. Back to the main interface, click “Apply” and “Proceed” to commit the pending operation.


Wait for a while, the Server C drive will be extended with the unallocated space. Moreover, if there is no unallocated space, you can try the “Allocate Free Space” feature to directly assign some free space from one partition to another.

Allocate Free Space From D To C Drive


If you are excellent at running commands, you can use DiskPart to extend Server C drive. If not, AOMEI Partition Assistant Server is a better choice. No matter whether there is (adjacent) unallocated space or not, it provides corresponding solutions. Except for the functions above, there are still many other great functions, such as split partition, clone disk, clone partition, check the partition for bad sectors, clone disk, and more.

Besides, the AOMEI Partition Assistant Unlimited and AOMEI Partition Assistant Technician have a useful feature, Create Portable Version, which can create AOMEI Partition Assistant to a removable device, such as USB flash drive. Then, you can connect the device to other computers and run AOMEI Partition Assistant from the device without installation. 

Dervish · Staff Editor
Dervish is an English editor of AOMEI Technology; He is delicated to offering users easy and effecitve solutions for issuses related to disks and partitoins. In his spare time, he enjoy wathcning films, playing footable, traveling and so on.