virt-v2v generally converts machines without issue but when there's a problem it is way too efficient in cleaning up the disk images which makes debugging of the problematic disk images harder because you often then need to do a manual dd of the images over the network. A --no-cleanup would be very useful for debugging of disk images that have conversion issues so as to make it easier to fix issues or investigate the disk images using something like guestfish or virt-rescue
RFE, moving to the upstream tracker.