Is Btrfs vulnerable to RAID write hole effect?

Question

If not, does it mean that Btrfs in RAID mode is fully resistant to power failure?

Answer 1

Yes, unfortunately btrfs RAID5/6 still suffers from the write hole (10/2015).

The one missing piece, from a reliability point of view, is that it is still vulnerable to the parity RAID "write hole", where a partial write as a result of a power failure may result in inconsistent parity data.

https://btrfs.wiki.kernel.org/index.php/RAID56

However, if you're reading this in the future, this may already be fixed. (Btw. ZFS does not suffer from this issue.)

Answer 2

From what I've read on Btrfs, the nature of the filesystem itself makes it resistant against power failures in most situations, especially in a RAID configuration. I say most because there's always a situation that could cause data loss (say, power outage results in a spike when power comes back online, toasting your disk(s).)