It seems kind of like hard linking but with copy-on-write for the underlying data, so you'll get near-instant file copies and writing into the middle of them wi

It seems kind of like hard linking but with copy-on-write for the underlying data, so you'll get near-instant file copies and writing into the middle of them will also be near-instant. All of this happens under the covers already if you have dedup turned on, but this allows utilities (gnu cp might be taught to opportunistically and transparently use the new clone zfs syscalls, because there is no downside and only upside) and applications to tell zfs that "these blocks are going to be the same as those" without zfs needing to hash all the new blocks and compare them. Aditionally, for finer control, ranges of blocks can be cloned, not just entire files. I can't tell from the github issue, can this manual dedup / block cloning be turned on if you're not already using dedup on a dataset? Last time I set up zfs, I was warned that dedup took gobs of memory, so I didn't turn it on.