Re: degraded raid 6 (1 bad drive) showing up inactive, only spares

[NeilBrown <neilb@suse.de>]

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On Sun, 17 Jun 2012 17:52:07 +0200 Martin Ziler <martin.ziler@googlemail.com>
wrote:

> Hello everybody,
> 
> long time no seen. As I was unable to find a permutation that would result in an fsck-output that looks ok I generated the 360.000 permutations using Neil's shell script. I then composed a little script that would try a permutation, do the fsck, stop the raid an go on with the new possibility and inserted the fsck-output into a text-file. The whole 360.000 permutations just recently finished - after some 6 days of building and fscking. I have not yet analyzed the output. I did however search for the term "clean" as a positive result would possibly contain that term.
> 
> I got 711 different drive-combinations that will result in this: /dev/md0: clean, 204968/849158144 files, 3394436623/3396621312 blocks.
> 
> If there really is only one working drive order, I guess I am pretty much doomed. I do hope I'll be able to rule out a large portion of those results before going into some more detail. I did get it correct, though, that there is only one possible order resulting in a working array? I gotta figure out how to analyze the output file now. It's 125 MB. I guess I'll probably split it and load it into my spreadsheet. In one go I'd stumble across the 1.000.000 row-limit.
> 
> regards,
> 
> Martin

Yes, there is only one correct order.

711 is very close to 720 which is 6!  I wonder if that is significant.

Maybe you need "fsck -n -f" to force it to do a more thorough check even
though the fs appears to be clean.

If you "echo check > /sys/block/mdXX/md/sync_action", wait 30 seconds or so,
then "echo idle > ......", then check "mismatch_cnt", the correct ordering
should have a significantly lower number - probably zero.
Other orders will have a high number.

NeilBrown


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