I am already a convert - the destination is ZFS, its great. Problem is all this legacy stuff, spanning many years, many times moved / duplicated from disk to disk etc, although its all on EXT4 now, which seems pretty good, but in the past... So at times I am going to need to work out which are the damaged versions manually. But I hope to hone it down to a few files with the rest all matching from version to version (hopefully a few that is, we will see).