On Feb 4, 2014, at 12:23 AM, James Hogarth <james.hogarth@gmail.com> wrote:

The other fun thing I encountered the other day is that cp --reflink=always still doesn't work across mount points even if they are part of the same btrfs pool and therefore capable of using COW between subvolumes.


There are patches upstream for this. I'm running 3.14rc1 which has a large pile of Btrfs patches, but reflink between mounted subvols is still not yet possible. The workaround is to mount a subvolume they have in common and then it works.

Chris Murphy