From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from asav21.altibox.net ([109.247.116.8]:54155 "EHLO asav21.altibox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752365Ab3KTKol (ORCPT ); Wed, 20 Nov 2013 05:44:41 -0500 Message-ID: <528C9297.9030801@hesbynett.no> Date: Wed, 20 Nov 2013 11:44:39 +0100 From: David Brown MIME-Version: 1.0 To: Piergiorgio Sartor , Andrea Mazzoleni CC: linux-raid@vger.kernel.org, linux-btrfs@vger.kernel.org, hpa@zytor.com, creamyfish@gmail.com Subject: Re: Triple parity and beyond References: <20131119181237.GA3666@lazy.lzy> In-Reply-To: <20131119181237.GA3666@lazy.lzy> Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 19/11/13 19:12, Piergiorgio Sartor wrote: > On Mon, Nov 18, 2013 at 11:08:59PM +0100, Andrea Mazzoleni wrote: > > Hi Andrea, > > great job, this was exactly what I was looking for. > > Do you know if there is a "fast" way not to correct > errors, but to find them? > > In RAID-6 (as per raid6check) there is an easy way > to verify where an HDD has incorrect data. > 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. > I suspect, for each 2 parity block it should be > possible to find 1 error (and if this is true, then > quad parity is more attractive than triple one). > > Furthermore, my second (of first) target would > be something like: http://www.symform.com/blog/tag/raid-96/ > > Which uses 32 parities (out of 96 "disks"). I believe Andrea's matrix is extensible as long as you have no more than 257 disks in total. A mere 32 parities should not be a problem :-) mvh., David > > Keep going!!! > > bye, > > pg > >> >> Ciao, >> Andrea >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-raid" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >