From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Robinson Subject: Re: emergency call for help: raid5 fallen apart Date: Thu, 25 Feb 2010 18:31:35 +0000 Message-ID: <4B86C207.6030304@anonymous.org.uk> References: <4B853DB7.1060406@xunil.at> <4B854040.5080603@xunil.at> <20100224152228.GB11039@cthulhu.home.robinhill.me.uk> <4B85467C.5020008@xunil.at> <4B855621.5010000@xunil.at> <4B855987.1010605@xunil.at> <4B855B8C.8080802@xunil.at> <4B862F2C.5030302@texsoft.it> <4B86A943.3040804@anonymous.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Linux RAID List-Id: linux-raid.ids On 25/02/2010 17:41, Dawning Sky wrote: > On Thu, Feb 25, 2010 at 8:45 AM, John Robinson > wrote: >> On 25/02/2010 08:05, Giovanni Tessore wrote: >> [...] >> I do think we urgently need the hot reconstruction/recovery feature, so >> failing drives can be recovered to fresh drives with two sources of data, >> i.e. both the failing drive and the remaining drives in the array, giving us >> two chances of recovering every sector. > > I was one of those 4 cases in the part month. I would have certainly > benefited from this when I tried to replace a failing drive on my old > raid-5. But I think actually the redundancy you desired can be > achieved by running a raid-6 at the degraded mode (with 1 missing > drive). > > Do I miss something? If this is the case, shouldn't we all > be doing this instead of using the raid-5? I think you must be missing something, yes. RAID-6 with one drive missing would have 2 chances of recovering each sector, but then so does RAID-5 with no drives missing. In either case, lose a drive and you need every sector on the remaining drives to be good to complete the reconstruction and keep the array up. Cheers, John.