Re: Data scribbling for raid6 is wrong?

[Tao Guo <glorioustao@xxxxxxxxx>]

Thanks, excellent article.

On Thu, Dec 15, 2011 at 12:27 PM, NeilBrown <neilb@xxxxxxx> wrote:
> On Thu, 15 Dec 2011 11:15:42 +0800 Tao Guo <glorioustao@xxxxxxxxx> wrote:
>
>> Hi all,
>>
>> Today I checked the raid6's scribbling code, and I think there may be
>> some improvements to handle bad sectors:
>
> I think the common term is "scrubbing" rather than "scribbling".
>
>>
>> If we have one bad sector(with corrupted data) in the data block,
>> scribbling thread will find parity mismatch and will try to
>> recompute&rewrite P&Q, but that will cause final data loss.
>> Since we have P & Q,  actually we can try to use them and find out the
>> wrong data block then fix it.
>>
>> But the algorithm to find the bad data block seems not
>> straightforward... Does anyone know if there is any paper discussed
>> this issue before?
>>
>> Update: I just found there is one talk about this in FAST08:
>> http://www.usenix.org/events/fast08/tech/krioukov.html.
>> But that approach will add checksums.etc. For bare-bones raid6, does
>> any guru have any better ideas?
>
> http://neil.brown.name/blog/20100211050355
>
> NeilBrown
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