On Fri, Dec 23, 2016 at 11:56:34AM +1100, Eyal Lebedinsky wrote:

From time to time I get non-zero mismatch_count in the weekly scrub. The way I handle
it is to run a check around the stripe (I have a background job printing the mismatch
count and /proc/mdstat regularly) which should report the same count.

I now drill into the fs to find which files use this area, deal with them and delete
the bad ones. I then run a repair on that small area.

I now found about raid6check which can actually tell me which disk holds the bad data.
This is something raid6 should be able to do assuming a single error.
Hoping it is one bad disk, the simple solution now is to recover the bad stripe on
that disk.

Will a 'repair' rewrite the bad disk or just create fresh P+Q which may just make the
bad data invisible to a 'check'? I recall this being the case in the past.

"repair" should fix the data which is assumed
to be wrong.
It should not simply correct P+Q, but really
find out which disk is not OK and fix it.

'man md' still says
	For RAID5/RAID6 new parity blocks are written
I think RAID6 can do better.

TIA

-- 
Eyal Lebedinsky (eyal@eyal.emu.id.au)
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

-- 

piergiorgio