Scrubbing with BTRFS Raid 5
Thanks again for the added info; very helpful.
I want to keep playing around with BTRFSS RAID 5 and testing with it... assuming I have a drive with bad blocks, or let's say some inconsistent parity am I right in assuming that a) a btrfs scrub operation will not fix the stripes with bad parity and b) a balance operation will not be successful? Or would a balance operation work to re-write parity?
Graham Fleming posted on Tue, 21 Jan 2014 10:03:26 -0800 as excerpted:
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I want to keep playing around with BTRFSS RAID 5 and testing with it... assuming I have a drive with bad blocks, or let's say some inconsistent parity am I right in assuming that a) a btrfs scrub operation will not fix the stripes with bad parity
What I know is that it is said btrfs scrub doesn't work with btrfs raid5/6 yet. I don't know how it actually fails (tho I'd hope it simply returns an error to the effect that it doesn't work with raid5/6 yet) as I've not actually tried that mode, here.
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and b) a balance operation will not be
successful? Or would a balance operation work to re-write parity?
Balance actually rewrites everything (well, everything matching its filters if a filtered balance is used, everything, if not), so it should rewrite parity correctly.
AFAIK, all the writing works and routine read works. It's the error recovery that's still only partially implemented. Since reading just reads data, not parity unless there's a dropped device or the like to recover from, as long as all devices are active and there's a good copy of the data (based on btrfs checksumming) to read, the rebalance should just use and rewrite that, ignoring the bad parity.
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Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman