Re: [Qemu-devel] Comparison of virtual disks?

[Paolo Bonzini <pbonzini@redhat.com>]

On 04/05/2015 13:14, Max Reitz wrote:
> I'm sorry, but I don't know whether such a chart exists (the closest
> thing I know is http://en.wikipedia.org/wiki/Category:Disk_images -
> which is not very close...). However, the general assumption we as
> developers are working with is that if the user's top priority is
> performance, they should use raw; and if they want to use all of the
> features qemu's block layer provides, they should use qcow2. All other
> formats are implemented merely for compatibility and ideally they should
> not be used for running VMs, but only for converting them to qcow2 using
> qemu-img convert.

In addition to this, there are a bunch of image formats that have good
read performance: I can think of vhdx, vmdk, vdi.  These can be used as
backing images for qcow2, for example the virt-v2v tool uses this trick
to convert Hyper-V and VMware images without copying them first.

Paolo