A hash is often use for an online algorithm. If you know the hash you know there is a potential for dedupe, and you can do a byte for byte comparison. I suppose you could use size as a prefilter for dedupe. This is if you do dedupe on a file level. Dedupe on block level doesn&#x27;t care about the content, only the blocks, and it&#x27;s not unusual to see for instance mp3 files with the same mp3 stream but different metadata. You cannot do the latter without hashing.