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posted by cmn32480 on Sunday August 07 2016, @02:38PM   Printer-friendly
from the how-bad-could-it-really-be dept.

The nice feller over at phoronix brings us this handy to have bit of info:

It turns out the RAID5 and RAID6 code for the Btrfs file-system's built-in RAID support is faulty and users should not be making use of it if you care about your data.

There has been this mailing list thread since the end of July about Btrfs scrub recalculating the wrong parity in RAID5. The wrong parity and unrecoverable errors has been confirmed by multiple parties. The Btrfs RAID 5/6 code has been called as much as fatally flawed -- "more or less fatally flawed, and a full scrap and rewrite to an entirely different raid56 mode on-disk format may be necessary to fix it. And what's even clearer is that people /really/ shouldn't be using raid56 mode for anything but testing with throw-away data, at this point. Anything else is simply irresponsible."

Just as well I haven't gotten around to trying it then.


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  • (Score: 1, Informative) by Anonymous Coward on Sunday August 07 2016, @06:01PM

    by Anonymous Coward on Sunday August 07 2016, @06:01PM (#385009)

    Different AC here, but I've had similar experiences with btrfs killing itself. It was on a fresh install of opensuse, I believe, and it didn't last a week before it wouldn't boot. Nothing fancy, no raid or the like, just pure defaults, hence why I used it at all. Didn't inspire confidence in the file system or the distro that picked it.

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  • (Score: 2) by rleigh on Sunday August 07 2016, @06:48PM

    by rleigh (4887) on Sunday August 07 2016, @06:48PM (#385017) Homepage

    You most likely hit the unbalancing issue which makes it go read-only. I've seen this repeatedly. A rebalance would fix it, though it takes ages and kills the system's performance while it grinds away. Note I use "issue" rather than "bug" because it's more of a design flaw, though the implementation is undoubtedly also defective. Search for "btrfs read only balance" for a whole lot of detail about it. When I initially read that SuSE was going to default to Btrfs my initial reaction was utter disbelief; how on earth they justified doing that I hate to think.

    • (Score: 0) by Anonymous Coward on Sunday August 07 2016, @08:54PM

      by Anonymous Coward on Sunday August 07 2016, @08:54PM (#385042)

      It's also default on SUSE commercial distro that is supported until 2030 or something, so .... but you can also select Ext4 or XFS too. But some influential people were pushing for it so SUSE is stuck with it now - hopefully it's not too buggy!

      • (Score: 0) by Anonymous Coward on Monday August 08 2016, @10:45PM

        by Anonymous Coward on Monday August 08 2016, @10:45PM (#385519)

        Commercial distro, eh? As in commercial support? Great way to get people to call you for support would be to have the file system hose itself seemingly at random, especially at the times they are must desperate.

    • (Score: 0) by Anonymous Coward on Sunday August 07 2016, @09:12PM

      by Anonymous Coward on Sunday August 07 2016, @09:12PM (#385044)

      Nope, in my SuSE case, it was a single disk VM and mounting it into another VM with btrfs support reported errors when running through the diagnostic procedure on the wiki. But, if you have stupid things pop up like rebalancing in normal use in less than a week on a single disk after light use, assuming that was even the problem instead of actual corruption, then btrfs is total garbage and SuSE is too for having garbage defaults.