[libvirt-users] VM with transient disk

[Eric Blake]

On 10/31/2011 12:54 AM, Till Mossakowski wrote:
> Hi Osier,
>
> are there other hypervisors supporting it?

Not yet.  It was added to the XML with intents to support it in at least 
ESX and qemu, but neither driver has completed this support of the XML 
yet.  And it looks like 0.9.7 won't have it either, now that we are in 
feature freeze for the next release.  I'll get to it eventually, but I 
would welcome anyone else trying to contribute patches in the meantime, 
since I have been distracted by bug fixes lately (fixing any existing 
but broken behavior tends to take priority over implementing new behavior).

>
> And what about qemu's option "snapshot=on" ?

Unreliable.  It won't work with SELinux (since qemu tries to create the 
snapshot on /tmp), and it makes your guest unmigratable.  I think that 
it is easier to have libvirt use qemu-img to create a qcow2 wrapper 
prior to booting the guest, at which point the solution is easier to 
control from an sVirt perspective, and is more likely to allow us to 
figure out a way to make things work with migration (at least, I'm 
hoping I can figure out how to migrate a guest with a transient disk).

But if you want to use qemu's snapshot=on in the meantime, you can use 
the <qemu:commandline> namespace XML to add it.

-- 
Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org