If the FS implements snapshots "down low" you get COW efficient, and pretty much lock-free atomic "it's done" -if you run userspace "get me the difference" then

If the FS implements snapshots "down low" you get COW efficient, and pretty much lock-free atomic "it's done" -if you run userspace "get me the difference" then it has all kinds of runtime costs and risks. That said, rsync is pretty good. Your J model can't get more memory. And you look to be right, its the OS it comes with and thats it. The NAS you have is the best NAS sometimes. It's all very well positing better ones, but they aren't the one you have: So make the most of it.