From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Janos Haar" Subject: Re: Suggestion needed for fixing RAID6 Date: Sat, 1 May 2010 23:44:04 +0200 Message-ID: <154b01cae977$6e09da80$0400a8c0@dcccs> References: <626601cae203$dae35030$0400a8c0@dcccs> <20100423065143.GA17743@maude.comedia.it> <695a01cae2c1$a72907d0$0400a8c0@dcccs> <4BD193D0.5080003@shiftmail.org> <717901cae3e5$6a5fa730$0400a8c0@dcccs> <4BD3751A.5000403@shiftmail.org> <756601cae45e$213d6190$0400a8c0@dcccs> <4BD569E2.7010409@shiftmail.org> <7a3e01cae53f$684122c0$0400a8c0@dcccs> <4BD5C51E.9040207@shiftmail.org> <80a201cae621$684daa30$0400a8c0@dcccs> <4BD76CF6.5020804@shiftmail.org> <20100428113732.03486490@notabene.brown> <4BD830B0.1080406@shiftmail.org> <025e01cae6d7$30bb7870$0400a8c0@dcccs> <4BD843D4.7030700@shiftmail.org> <062001cae771$545e0910$0400a8c0@dcccs> <4BD9A41E.9050009@shiftmail.org> <0c1201cae7e0$01f9a930$0400a8c0@dcccs> <4BDA0F88.70907@shiftmail.org> <0d6401cae82c$da8b5590$0400a8c0@dcccs> <4BDB6DB6.5020306@sh iftmail.org> <12cf01cae911$f0d92940$0400a8c0@dcccs> <4BDC6217.9000209@shiftmail.org> 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: MRK Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids ----- Original Message ----- From: "MRK" To: "Janos Haar" Cc: Sent: Saturday, May 01, 2010 7:17 PM Subject: Re: Suggestion needed for fixing RAID6 > On 05/01/2010 11:37 AM, Janos Haar wrote: >> Whoever, the sync_min option generally solves my problem, becasue i can >> build up the missing disk from the 90% wich is good enough for me. :-) > > Are you sure? How do you do that? > Resyncing a specific part is easy, replicating to a spare a specific part > is not. If the disk you want to replace was 100% made of parity data that > would be easy, you do that with a resync after replacing the disk, maybe > multiple resyncs region by region, but in your case it is not made of only > parity data. Only raid3 and 4 separate parity data from actual data, raid6 > instead finely interleaves them. > If you are thinking about replacing a disk with a new one (full of zeroes) > and then resyncing manually region by region, you will destroy your data. > Because in those chunks where the new disk acts as "actual data" the > parity will be recomputed based on your newly introduced zeroes, and it > will overwrite the parity data you had on the good disks, making recovery > impossible from that point on. > You really need to do the replication to a spare as a single step, from > the beginning to the end. You cannot use sync_min and sync_max for that > purpose. You are right again, or at least close. :-) I have the missing sdd4 wich is 98% correctly rebuilt allready. But you are right, because the sync_min option not works for rebuilding disks, only for resyncing. (it is too smart to do the trick for me) > I think... unless bitmaps really do some magic in this, flagging the newly > introduced disk as more recent than parity data... but do they really do > this? people correct me if I'm wrong. Bitmap manipulation should work. I think i know how to do that, but the data is more important than try it on my own. I want to wait until somebody support this. ... or somebody have another good idea? The general problem is, i have one single-degraded RAID6 + 2 badblock disk inside wich have bads in different location. The big question is how to keep the integrity or how to do the rebuild by 2 step instead of one continous? Thanks again Janos > -- > 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