RAID56 - btrfs Wiki https://btrfs.wiki.kernel.org/index.php/RAID56
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今見てみると、
> From 3.19, the recovery and rebuild code was integrated. This brings the implementation to the point where it should be usable for most purposes. Since this is new code, you should expect it to stabilize over the next couple of kernel releases.
と書かれているので、Linux 4.1までは待てということなんだろうか。
