>> I think the buzzword you want is dedup. > dedup works at the file level. Here we're talking about files that are > highly similar but not identical. I don't want to rewrite an entire file > that's 99% identical to the new file form, I just want to write a small > set of changes. I'd use ZFS to keep track of which blocks change over time. > > I've been asking around, and it seems this capability doesn't exist > *anywhere*. Check this link. https://blogs.oracle.com/bonwick/entry/zfs_dedup ... *What to dedup: Files, blocks, or bytes?* Data can be deduplicated at the level of files, blocks, or bytes. ...