From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Janos Haar" Subject: Re: Suggestion needed for fixing RAID6 Date: Fri, 23 Apr 2010 10:47:47 +0200 Message-ID: <695a01cae2c1$a72907d0$0400a8c0@dcccs> References: <626601cae203$dae35030$0400a8c0@dcccs> <20100423065143.GA17743@maude.comedia.it> Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=response Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: Luca Berra Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids ----- Original Message ----- From: "Luca Berra" To: Sent: Friday, April 23, 2010 8:51 AM Subject: Re: Suggestion needed for fixing RAID6 > On Thu, Apr 22, 2010 at 12:09:08PM +0200, Janos Haar wrote: >> Hello Neil, list, >> >> I am trying to fix one RAID6 array wich have 12x1.5TB (samsung) drives. >> Actually the array have 1 missing drive, and 3 wich have some bad >> sectors! >> Genearlly because it is RAID6 there is no data lost, because the bad >> sectors are not in one address line, but i can't rebuild the missing >> drive, because the kernel drops out the bad sector-drives one by one >> during the rebuild process. > > I would seriously consider moving the data out of that array and dumping > all drives from that batch, and this is gonna be painful because you > must watch drives being dropped and add them back, and yes you need the > resources to store the data. > > ddrescue won't obviously work, since it will mask read errors and turn > those into data corruption > > the raid 1 trick wont work, as you noted > > another option could be using the device mapper snapshot-merge target > (writable snapshot), which iirc is a 2.6.33+ feature > look at > http://smorgasbord.gavagai.nl/2010/03/online-merging-of-cow-volumes-with-dm-snapshot/ > for hints. > btw i have no clue how the scsi error will travel thru the dm layer. > L. ...or cowloop! :-) This is a good idea! :-) Thank you. I have another one: re-create the array (--assume-clean) with external bitmap, than drop the missing drive. Than manually manipulate the bitmap file to re-sync only the last 10% wich is good enough for me... Thanks again, Janos > > -- > Luca Berra -- bluca@comedia.it > Communication Media & Services S.r.l. > /"\ > \ / ASCII RIBBON CAMPAIGN > X AGAINST HTML MAIL > / \ > -- > 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