>>> One thing I would like to see is copy-on-write hard-links. The hard-links >>> that span snapshots should be possible, but they should be copy-on-write, >>> i.e. as soon as hard-linked file that spans snapshots is written, the >>> snapshot that wrote it should have it's own forked copy henceforth. >> >> There are sym-links, hard-links, and ref-links. Cross device symlinks >> are trivial. Cross device hardlinks are evil. Cross device ref-links >> are just plain smart (and are at least partitially implemented in >> btrfs; does bcp work across subvolumes?). :) > > Last time I asked a similar question, there was no equivalent thing to COW > hard-links, across snapshots or otherwise. Hard-links spanning physical > devices don't make sense. Hard-links spanning snapshots, however, do. In > fact, I would intuitively expect that a snapshot contains only COW > hard-links which would get COW-ed from both the head and the snapshot. "COW hardlinks" are ref-links (as far as I'm concerned). I said partially implemented, because that's exactly what a snapshot is. I'm just not certain whether bcp works across subvolumes or not. An actual hardlink (i.e., all writes appear in all hardlinks) across any file-system-like-structure (including subvolumes and snapshots) is insane, for the reasons that I'm sure David offered to explain. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
