Resizing a system or data disk in a virtual machine
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.
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.
à this gives you a list of the available partitions
select volume x
à select the partition number you want to increase
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
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.