Btrfs RAID5/RAID6 Support Finally Get Fixed

Written by Michael Larabel in Linux Storage on 16 November 2016 at 02:30 PM EST. 12 Comments
Over the summer we wrote about Btrfs RAID 5/6 code was found to be unsafe and likely would need a rewrite. Months later, patches have finally emerged to fix the faulty Btrfs RAID 5/6 code.

Qu Wenruo on Tuesday posted patches to fix the "famous RAID5/6 scrub error" and he went on to explain the situation, "Unlike many of us(including myself) assumed, it's not a timed bomb buried deeply into the RAID5/6 code, but a race condition in scrub recovery code. The problem is not found because normal mirror based profiles aren't affected by the race, since they are independent with each other. Although this time the fix doesn't affect the scrub code much, it should warn us that current scrub code is really hard to maintain."

With that said, two patches across just under 200 lines of code is able to fix this issue. Details on the linux-btrfs list. Hopefully these patches will end up getting merged for the Linux 4.10 kernel.

Update: Pardon the confusion, it turns out Btrfs RAID 5/6 code is only partially fixed.
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Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via

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