Btrfs support Copy-On-Write. I tried to use that feature to clone a directory:
cp -R --reflink=always foo_directory foo_directory.mirror
I expected the command to finish almost instantly (like a
btrfs subvolume snapshot), but the
cp command seems to perform a slow, standard copy.
According to the man page, I would expected
--reflink=always to enforce Copy-On-Write:
--reflink[=always]is specified, perform a lightweight copy, where the data blocks are copied only when modified. If this is not possible the copy fails, or if
--reflink=autois specified, fall back to a standard copy.
- Do you know why
- What options (or other commands) should I use instead?