ZFS promises dedupe and super-simple snap synch to another host.

What I liked it for over e4 is the far greater inode count per file, as my backup setup was doing hardlink(1) and running into the boundary a lot.

Now I like its trivial snapshotting as a periodic rollback target on my file server to recover from occasional oopses; hook the .snaps up to a smbd and people can grab their own files back from the brink.

I still use like 90% e4 though. More stable and reliable than xfs, it's good for everything you value.