I'm running a rather default Kubuntu 16.10 setup with btrfs. To my dismay and surprise I found that copying files is not instant as I would expect with btrfs.

I need to manually force copy-on-write via cp --reflink for this to work. Why is this the case and how can I correct this behavior?


It is a normal behavior. If you use mv, it will do it instantly. If you copy, it is supposed to be a "real" copy.

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    why would that be normal on a copy on write FS? Any copy on a copy on write FS should typically be near instant? – Nik May 9 '17 at 21:03
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    Ah, I just saw you actual answer was given as comment to my post. Thanks, the mentioned link unix.stackexchange.com/questions/80351/… explains what's going on – Nik May 9 '17 at 21:08
  • Giving this more though though, I still wonder: I don't want any copy operation on my FS ever to do anything but copy on write, never mind if it was triggered by cp, or file manager or by a software ... any way to achieve this? – Nik May 10 '17 at 21:16
  • @Nik use an alias like an answer on your linked question? – phuclv May 9 '18 at 4:21

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