Re: Suggestion needed for fixing RAID6

["Janos Haar" <janos.haar@netcenter.hu>]

Hi,

----- Original Message ----- 
From: "Stefan /*St0fF*/ Hübner" <stefan.huebner@stud.tu-ilmenau.de>
To: "Janos Haar" <janos.haar@netcenter.hu>
Sent: Thursday, April 22, 2010 10:18 PM
Subject: Re: Suggestion needed for fixing RAID6


> Hi Janos,
>
> I'd ddrescue the failing drives one by one to replacement drives.  Set a
> very high retry-count for this action.

I know what am i doing, trust me. ;-)
I have much more professional tools for this than the ddrescue, and i have
the list of defective sectors as well.
Now i am imaging the second of the failing drives, and this one have >1800
failing sectors.

>
> The logfile ddrescue creates shows the unreadable sectors afterwards.
> The hard part would now be to incorporate the raid-algorithm into some
> tool to just restore the missing sectors...

I can do that, but it is not a good game for 15TB array or even some hundred
of sectors to fix by hand....
The linux md knows how to recalculate these errors, i want to find this
way....somehow...
I am thinking of making RAID1 from the defective drives, and if the kernel
will re-write the sectors, the copy will get it.
But i don't know how to prevent the copy to read it. :-/

Thanks for your suggestions,

Janos

>
> I hope this helps a bit.
> Stefan
>
> Am 22.04.2010 12:09, schrieb Janos Haar:
>> Hello Neil, list,
>>
>> I am trying to fix one RAID6 array wich have 12x1.5TB (samsung) drives.
>> Actually the array have 1 missing drive, and 3 wich have some bad
>> sectors!
>> Genearlly because it is RAID6 there is no data lost, because the bad
>> sectors are not in one address line, but i can't rebuild the missing
>> drive, because the kernel drops out the bad sector-drives one by one
>> during the rebuild process.
>>
>> My question is, there is any way, to force the array to keep the members
>> in even if have some reading errors?
>> Or is there a way to re-add the bad sector drives after the kernel
>> dropped out without stopping the rebuild process?
>> In normal way after 18 hour sync, @ 97.9% the 3rd drive is always
>> dropped out and the rebuild stops.
>>
>> Thanks,
>> Janos Haar
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