[libvirt-users] libvirt, lvm thin provisioning

[Eric Blake]

On 12/03/2013 12:37 PM, Michael Mol wrote:

> A pity. Thin provisioning would be (as I see it) the first step to
> whole-VM snapshots as found in systems like VMWare ESX. I'd love to be
> able to pull that off using Linux/QEMU/KVM. Or at least be able to
> snapshot a running VM's disk to be able to pull backups off the
> snapshot without interrupting service in the VM guests.

Ah, but you already CAN do that.  Libvirt external snapshots (since
libvirt 1.0.5, or even earlier if you don't care about machine state but
just disk state) coupled with qemu 1.3 or newer is perfectly able to
create qcow2 chains such that you can do a backup of the snapshot
without any downtime to the guest.  Admittedly, keeping things optimal
so that the qcow2 chain doesn't grow without bounds is a bit harder
problem, and qemu 1.7 has added some new functionality not yet
integrated into libvirt to make life easier for taking snapshots without
having to track the cleanup efforts.  But your claim that libvirt can't
do online backups the way ESX can aren't quite true :)

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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