Btrfs allows migration from ext4 with a rather good rollback strategy... Post-migration, a complete disk image of the original ext4 disk will exist within the

Btrfs allows migration from ext4 with a rather good rollback strategy... Post-migration, a complete disk image of the original ext4 disk will exist within the new filesystem, using no additional disk space due to the magic of copy-on-write. Why isn't the repair process the same? Fix the filesystem to get everything online asap, and leave a complete disk image of the old damaged filesystem so other recovery processes can be tried if necessary.