From mboxrd@z Thu Jan 1 00:00:00 1970 From: Piergiorgio Sartor Subject: Re: Triple parity and beyond Date: Wed, 20 Nov 2013 22:59:39 +0100 Message-ID: <20131120215939.GA2622@lazy.lzy> References: <20131119181237.GA3666@lazy.lzy> <528C9297.9030801@hesbynett.no> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <528C9297.9030801@hesbynett.no> Sender: linux-raid-owner@vger.kernel.org To: David Brown Cc: Piergiorgio Sartor , Andrea Mazzoleni , linux-raid@vger.kernel.org, linux-btrfs@vger.kernel.org, hpa@zytor.com, creamyfish@gmail.com List-Id: linux-raid.ids On Wed, Nov 20, 2013 at 11:44:39AM +0100, David Brown wrote: [...] > > In RAID-6 (as per raid6check) there is an easy way > > to verify where an HDD has incorrect data. > >=20 >=20 > I think the way to do that is just to generate the parity blocks from > the data blocks, and compare them to the existing parity blocks. Uhm, the generic RS decoder should try all the possible combination of erasure and so detect the error. This is unfeasible already with 3 parities, so there are faster algorithms, I believe: Peterson=E2=80=93Gorenstein=E2=80=93Zierler algorithm Berlekamp=E2=80=93Massey algorithm Nevertheless, I do not know too much about those, so I cannot state if they apply to the Cauchy matrix as explained here. bye, --=20 piergiorgio -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html