From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Tso Subject: Re: Redundancy check using "echo check > sync_action": error reporting? Date: Thu, 20 Mar 2008 14:02:41 -0400 Message-ID: <20080320180241.GJ13719@mit.edu> References: <47DD2CD7.2090802@tuxes.nl> <20080316161451.0d17fd22@szpak> <47E26775.3000500@tuxes.nl> <20080320134747.GA28114@cthulhu.home.robinhill.me.uk> <47E2725C.1020206@tuxes.nl> <20080320163551.GG13719@mit.edu> <20080320173906.GN32242@skl-net.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20080320173906.GN32242@skl-net.de> Sender: linux-raid-owner@vger.kernel.org To: Andre Noll Cc: Bas van Schaik , linux-raid@vger.kernel.org List-Id: linux-raid.ids On Thu, Mar 20, 2008 at 06:39:06PM +0100, Andre Noll wrote: > On 12:35, Theodore Tso wrote: > > > If a mismatch is detected in a RAID-6 configuration, it should be > > possible to figure out what should be fixed > > It can be figured out under the assumption that exactly one drive has > bad data and all other ones have good data. But that seems to be an > assumption that is hard to verify in reality. True, but it's what ECC memory does. :-) And most people agree that it's a useful thing to do with memory. If you do ECC syndrome checking on every read, and follow that up with periodic scrubbing so that you catch (and correct) errors quickly, it is a reasonable assumption to make. Obviously a warning should be given when you do this kind of ECC fixups, and if there is an increasing number of ECC fixups that are being done, that should set off alarms that maybe there is a hardware problem that needs to be addressed. Regards, - Ted