Re: [libvirt] [Qemu-devel] [RFC] qcow3 format in libvirt
Am 04.03.2013 um 14:09 hat Daniel P. Berrange geschrieben:
On Mon, Mar 04, 2013 at 01:58:12PM +0100, Ján Tomko wrote:
> Before posting another version of my patches [1], attempting to add
> support for the new qcow format to libvirt, I would like to know if this
> sounds reasonable:
>
> A new format named 'qcow3' would be added, along with a <features>
> sub-element for target.
>
> <volume>
> <name>qcow3test</name>
> <source>
> </source>
> <capacity unit='GiB'>8</capacity>
> <target>
> <path>/var/lib/libvirt/images/qcow3test</path>
> <format type='qcow3'/>
> <features>
> <lazy_refcounts/>
> </features>
> </target>
> </volume>
>
> I think that libvirt shouldn't care if the features are compatible or
> incompatible, as we don't know what features are supported by the
> hypervisor. Would the features be any good as tri-state (on, off, default?).
>
> While the qcow3 format is handled by the qcow2 driver in QEMU,
> <driver name='qemu' type='qcow2'/> should be enough for
domains,
We should use qcow3 everywhere IMHO, regardless of whether qcow2
technically works in this context.
I think it makes much more sense to deal with it the way qemu does
instead of inventing new names. This has much more of an (incompatible)
feature flag than of a different image format. So to fit it in your
proposed syntax:
<target>
<path>/var/lib/libvirt/images/qcow3test</path>
<format type='qcow2'/>
<features>
<compat version="1.1" />
<lazy_refcounts/>
</features>
</target>
Or if you really think that you should refer to the inner workings of
qcow2, you can make it <version>3</version>.
But I guess you call all VMDKs just "vmdk", despite the fact that they
are really just a collection of different subformats. Right?
Kevin