From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfgang Denk Subject: Re: Huge values of mismatch_cnt on RAID 6 arrays under Fedora 18 Date: Thu, 31 Jan 2013 19:36:06 +0100 Message-ID: <20130131183606.E4C23200276@gemini.denx.de> References: <20130127192656.634892005AD@gemini.denx.de> <20130128173704.GA2329@lazy.lzy> <20130128190035.D943A294BAB@gemini.denx.de> <20130128191041.8E962200607@gemini.denx.de> <20130128192256.GB13803@lazy.lzy> <20130128201947.2B615200607@gemini.denx.de> <20130128204422.GA14115@lazy.lzy> <20130128231840.03C37203AD5@gemini.denx.de> <20130129175720.GB2396@lazy.lzy> <20130129184309.D65DD2A1846@gemini.denx.de> <20130129202433.GB7005@lazy.lzy> <20130131121220.F3CA220059E@gemini.denx.de> <3DB28596-B1D6-48A9-9520-4CF9D367E39D@colorremedies.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Return-path: In-reply-to: <3DB28596-B1D6-48A9-9520-4CF9D367E39D@colorremedies.com> Sender: linux-raid-owner@vger.kernel.org To: Chris Murphy Cc: Piergiorgio Sartor , linux-raid@vger.kernel.org List-Id: linux-raid.ids Dear Chris Murphy, In message <3DB28596-B1D6-48A9-9520-4CF9D367E39D@colorremedies.com> you wrote: > > > After running a "repair" on the array, both "check" and "raid6test" > > would not report any further issues. > > Yes but this would be consistent with a derivative parity, written > to disk and then checked against an algorithm that expects derivative > parity. What happens if you go back to the old kernel before all the > problems were happening and you do a check? What happens if you go > back to a Fedora kernel you know exhibited the problem and you do a > check? I cannot test the exact old kernel I was running before any more; Fedora has released an update in the meantime, and they do not keep older updates around, only the very latest one - which is the same version as causes the problems. When using the (really old) kernel from the installation media, I see the same behaviour as with current mainline: I have to run a "repair", and then the array is, and remains, clean. With the current Fedora kernel, the first check will report errors which do not go away permanently, not even with a "repair". > Question for Piergiorgio is if check and raid6test use the same, or > independent, code for checking parity? My impression is that they must use different code - raid6test takes much, much longer and causes a much higher CPU load than running "check". > I think a bug needs to be filed with the information you have thus far. I did this, actually in parallel with reporting the issues here: https://bugzilla.redhat.com/show_bug.cgi?id=904831 I think the relevant Fedora people are on Cc:, but there was zero response so far; seems potential data loss is of no concern to the Fedora project :-( Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de You don't have to worry about me. I might have been born yesterday... but I stayed up all night.