I have to update one of client KVM QEMU host server for new kernel and libvirt. I need to do the backup and I'm using virt-clone as per command below. Its take around half and hour for my 62GB of VM to be clone. Example of virt-clone that Im using
virt-clone -o Ubuntu-Zimbra-Email -n Ubuntu-Zimbra-Email301210 -f /data/backup/Ubuntu-Zimbra-Email301210.qcow2
Ubuntu-Zimbra-Email = Name of the VM to be clone (need to shutdown the VM)
Ubuntu-Zimbra-Email301210 = Name of the new VM machine.
/data/backup/Ubuntu-Zimbra-Email301210.qcow2 = Directory where you want to put the VM file.
Replace the above thats suitable with your setup.
XML file for the clone machine is created under /etc/libvirt/qemu
You can read more about virt-clone here
virt-clone take sometimes. Im using screen so I can detach my terminal without worrying the connection will be lost. Command issues in Screen can be monitor.
Detach " Ctrl and A D
To return to session : screen -r