Both Mac and Windows already do memory compression. I don't know how ZFS works but the dedup I have seen runs in the background consuming minimal resources. I

Both Mac and Windows already do memory compression. I don't know how ZFS works but the dedup I have seen runs in the background consuming minimal resources. I would think if your mem-mapping a file that has been depdupped then its could just memap the already deduped block and cache in memory and not consume more memory if another file uses the same block and is memmapped but not sure if any OS does that.