Am 2011-08-26 16:08, schrieb Robin Hill:
> sda4 is still in the array, with some unreadable sectors. sdb4 is a
> spare because the resync failed due to unreadable sectors on
> sda4. You cannot add a disk to an array unless the data can all be
> read (or recovered if there's still enough redundancy).
Ah, now I got it.
I misinterpreted this:
md2 : active raid1 sdb4[2](S) sda4[0]
962454080 blocks [2/1] [U_]
I thought [U_] maps to the first line "sdb4 sda4" and somehow read
"sdb4 is UP and sda4 is down"
I could have seen it at
Number Major Minor RaidDevice State
0 8 4 0 active sync /dev/sda4
1 0 0 1 removed
2 8 20 - spare /dev/sdb4
but you know, panic ;-)
So basically I am where I was before swapping sdb: everything running
on sda, which has some corrupt sectors. Which may never have been
touched so far.
>> As far as I understand it might be possible to spot the defective
>> sectors and the related LV?
>>
> A read of the relevant block device (dd if=/dev/xxx of=/dev/null)
> will result in read errors for whichever block device contains the
> bad sectors. You could also probably map the sectors reported by
> the kernel to the position on the disk to tell what LV it.
There is only 350GB out of ~920GB mapped to active LVs. It might be
the case that the corrupt stuff isn't even mapped yet.
I once knew how to figure that out, I will have a closer look.
>> I have backups, yes ...
>>
> In which case the absolute safest option is just to recreate
> whatever arrays, PVs, LVs, etc. on sdb4 and restore the data,
> ignoring whatever's on sda4 currently.
I understand now, yes.
>> re-adding sda4 and starting such a check would be possible? Or
>> would a re-add damage things?
>>
> You can't add sda4 because it's already in the array.
Sure, now that I figured out the mentioned misunderstanding.
>> Should I shutdown the box for safety?
>>
> For absolute safety, yes, though I don't think the risk is too
> high at the moment, and I don't think things'll get any worse in
> the short term.
That sounds good for my weekend! Thanks ...
>> I am really feeling unsafe now, and getting another hdd for
>> swapping will take me at least until monday.
>>
>> (I would like to dd-rescue to another new disk to keep sdb, just
>> in case)
>>
> I doubt you'd be able to recover anything useful from sdb4 at the
> moment, but that's up to you.
Yep, also clear now.
I wait with that ddrescue-stuff anyway.
Thanks for your help!
Stefan
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