Re: [libvirt-users] Can I move the disk image of the guest while it is running?

On Wed, Feb 05, 2014 at 10:54:15PM +0100, Gergely Horváth wrote: > Thank you Eric, > > On 2014-02-05 17:23, Eric Blake wrote: > > Yes, live storage migration is possible; although at the moment, qemu is > > lacking a way to restart the operation if it fails midstream, so libvirt > > only allows the operation if you are willing to temporarily make your > > guest transient. > > What does this mean? Will I loose anything if - for example - there is > not enough space on the target device? As I understand it, no, you'll not lose anything. Here's some old notes for live backup with 'virsh blockcopy', this was after discussing with Eric http://kashyapc.fedorapeople.org/virt/lc-2012/live-backup-with-blockcopy.txt Currently due to QEMU's limitation, libvirt expects a domain to be trasient. Because, blockcopy jobs last forever until canceled, which implies that they should last across domain restarts if the domain were persistent. But qemu doesn't yet provide a way to restart a copy job on domain restart. So the trick is to temporarily make the domain transient > Or it will still use the original > disk image? > > AFAIK, a transient guest only means it will disappear after the > virtualisation session ends. The disk image stays intact, just it'll disappear from libvirt's view, hence you take a copy of your XML file below ('virsh dumpxml') does that > > > virsh dumpxml $dom > file > > virsh undefine $dom > > virsh blockcopy $dom /ssd/image.raw /hdd/image.raw \ > > --wait --verbose --pivot > > virsh define file > > I could not find anything about "pivot" or "pivoting"? What does --pivot > do in this case? When you "pivot", libvirt will use the new copy (i.e. /hdd/image.raw in this case), and this is done while the guest is running. Eric, please correct if I said something wrong.