I get a lot of questions of students and customers about resizing a virtual disk. This is the reason for this blog.

The following procedure will guide you step by step through the process of resizing (increasing) a disk of a virtual machine.

Before you make virtual hardware changes be sure you have taken a full backup of the virtual machine.

 

NOTE: If you do not want any troubles only increase the disk size. Decreasing can cause loss of data.

 

Flow

 

Increase Disk using diskpart

Step 1: Edit the virtual machine settings and increase the size of the disk (VMDK).

Step 2: Open the console of this virtual machine and start a command prompt.

Step 3: Start diskpart and execute following steps.

list volume
à this gives you a list of the available partitions

select volume x
à select the partition number you want to increase

extend
à this will add the empty disk space into the partition.

Now the partition has increased in size.

NOTE: On Windows 2008 this can be done via the Device Manager / Storage, but I have seen some weird things like showing incorrect partition sizes.

 

Increase Disk using Third Party tool

Since I have some great experiences with the Acronis Disk Director tool I will explain the steps to increase a disk using this tool. Another tool that can be used is e.g. GParted.

Step 1: Be sure you have a boot image (ISO) of the Acronis Disk Director Tool that supports your guest OS.

Step 2: Boot your virtual machine using the boot image ISO. Use the ESC button during booting your virtual machine to activate the “one time boo menu”

Step 3: Select the partition you want to increase and right mouse click on it. Then select “Resize Volume”

Step 4: Increase the disk space of the selected partitions by decreasing the unallocated space to 0

Step 5: After increasing the partition you have to commit the changes.

Step 6: Now you need to reboot your virtual machine after disconnecting the boot image.