From mboxrd@z Thu Jan 1 00:00:00 1970 From: Goswin von Brederlow Subject: Re: mismatch_cnt again Date: Sun, 08 Nov 2009 16:32:58 +0100 Message-ID: <87skcpav6d.fsf@frosties.localdomain> References: <4AF4C247.6050303@eyal.emu.id.au> <4AF4D323.6020108@panix.com> <4AF5268D.60900@eyal.emu.id.au> <4877c76c0911070008m789507f8h799d419287740ca5@mail.gmail.com> <87tyx6tpcb.fsf@frosties.localdomain> <4AF58B20.3000409@redhat.com> <4AF59F19.1080409@lazy.lzy> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: <4AF59F19.1080409@lazy.lzy> (Piergiorgio Sartor's message of "Sat, 07 Nov 2009 17:23:53 +0100") Sender: linux-raid-owner@vger.kernel.org To: Piergiorgio Sartor Cc: Doug Ledford , Goswin von Brederlow , Michael Evans , Eyal Lebedinsky , linux-raid list List-Id: linux-raid.ids Piergiorgio Sartor writes: > On 11/07/2009 03:58 PM, Doug Ledford wrote: > [...] >> I'm very quickly starting to become dubious of the current mismatch_cnt >> implementation. I think a kernel patch is in order and I may just work >> on that today. Here's the deal: a non-0 mismatch count is worthless if >> you don't also tell people *where* the mismatch is so they can >> investigate it and correct it. > > You're perfectly right. > > And this, again, fits in the discussion of RAID-6 error > check and, potentially, repair. > > Ideally the log should tell which (RAID) address has a > mismatch and, in case of RAID-6, if a specific device > could be faulty at that position. Actual in raid6 mode if one parity block is bad but the other is correct I would expect that to automatically repair the bad block, at least optionally. Same with a 3+ way mirror and one mirror being bad. In general if a block is bad and the kernel can isolate which block in a stripe is bad then it should repair it while checking. > This would be already quite a huge step forward in improving > the overall reliability of the RAID sub-system. > > Side note: in F11 there is this cron.weekly raid-check, but > nothing is reported (per email to root) in case of mismatch. > Is there any plan to add a such a facility? In Debian it is monthly, first sunday of the month. Takes too long to do weekly imho. > Thanks. > > bye, MfG Goswin