тут в прокс live-restore завезли:
"live-restore" allows starting a VM immediately from a backup snapshot, no
waiting for a long restore process. This is made possible with QEMU backing
images, i.e. data is read from the backup which is attached to the VM as a
drive, but new data is written to the destination, while a background process
('block-stream') copies over data in a linear fashion as well.