From mboxrd@z Thu Jan  1 00:00:00 1970
From: "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: mismatch_cnt questions
Date: Wed, 07 Mar 2007 22:34:13 -0800
Message-ID: <45EFAE65.9050608@zytor.com>
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To: Eyal Lebedinsky <eyal@eyal.emu.id.au>
Cc: Neil Brown <neilb@suse.de>, Christian Pernegger <pernegger@gmail.com>, linux-raid@vger.kernel.org
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Eyal Lebedinsky wrote:
> Neil Brown wrote:
> [trim Q re how resync fixes data]
>> For raid1 we 'fix' and inconsistency by arbitrarily choosing one copy
>> and writing it over all other copies.
>> For raid5 we assume the data is correct and update the parity.
> 
> Can raid6 identify the bad block (two parity blocks could allow this
> if only one block has bad data in a stripe)? If so, does it?
> 
> This will surely mean more value for raid6 than just the two-disk-failure
> protection.
> 

No.  It's not mathematically possible.

	-hpa