[libvirt] QEMU migration with LOCAL STORAGE

Hello, Libvirt consider it's safe to migrate a guest when its disks are readonly, or cache=none or has coherent cluster fs backend. But I've some questions over that: When migrating guests with LOCAL STORAGE, as qemu uses DRIVE MIRROR to migrate disk images, all storage data will migrate to dest by qemu. So, I don't find it necessary to let the disk cache be none, even its cache is not none, it's still safe to migrate. Is there any situation that destination VM can't see all completed writes? Regards, Lina