Grant McWilliams

Tech Virtualization Blog Virtual disk formats

Virtual disk formats

The problem with Virtualization systems is none of them want to standardize on one particular disk format. Actually they all do, they want their format to be the standard.

  • VMware has VMDK
  • QEMU has qcow and qcow2
  • UML has cow
  • Parallels has HDD
  • VirtualPC uses VHD
  • VirtualBox has VDI
  • Xen uses raw disk images

To make matters more confusing VirtualBox has some support for VMDK, Commercial Xen supports VHD, the open source Xen supports qcow2 and Qemu can convert between many formats. So what I'm doing about this is putting up a series of Howtos in the Tech -> Virtualization areas on how to convert and use various disk formats in different Virtualization systems. To start with I just put together the following two Howtos.

  1. How to convert Qemu images to VirtualBox
  2. How to convert raw disks to VirtualBox

In the future I'll add the following howtos (no timeline though)

  1. How to use Qemu disks in Xen
  2. How to convert VMware disks to Qemu, Xen, VirtualBox
  3. How to convert Parallels disks to Qemu, Xen, VirtualBox
  4. How to use LVM in Xen
  5. How to use raw disks in VirtualBox


The most irritating thing about all of these formats is that most are the same and have no advantage over the others. They're different just to be different.

Tech Virtualization Blog Virtual disk formats