On 3/9/13 11:39 PM, Jonathan Rogers wrote:
In an earlier implementation, I did call "cp --reflink=auto" once per regular file, preserving the behavior of copydir. On Btrfs, this works well, though slightly slower due to extra processes. AFAIK, there's no way to do something equivalent on ZFS without coming up with a much more complicated scheme involving both links and clones.
Chasing after the performance win of the copy acceleration seems worth it. We can't really do that if it results in an obvious behavior change though. If it takes a bit longer to do it file at a time, but that's the right thing to do, as long as it's still a net win this idea is still worthwhile.
I don't think it will be possible to implement a scheme that works on ZFS and addresses your concerns about file and directory handling that is not many times more complex than what I have so far. OTOH, I think the approach I have already implemented which calls an external command for each regular file to copy might be acceptable. Since I don't personally have much interest in using ZFS, I think I'm going to just focus on Btrfs for now.
Just be aware that OS specific features like this are a lot more likely to be accepted if they're demonstrated to work on two OSes. That's much better evidence that the API for the OS specific work is a good one.
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