nfs server migration hard disk

Hello, I migrate VMs from a cluster PVE 3 to a PVE 4. Ideally, it should use a backup / restore of each VM from the old node proxmox 3 (A), to the new node proxmox 4 (B). Here's an idea to have very little downtime : Migrate hard drives between each node with NFS storage, then, stop VM on old...