On Tue, Feb 16, 2010 at 11:57:00AM +0100, Michael wrote: > Hi Keld, > > if you do a smartctl -A on /dev/sdX you sould see something under > Current_Pending_Sector and Offline_Uncorrectable. > Your hard drive replaces the bad blocks with spare blocks as far as you > are write something to them. > > i have solved the resync issue by using > dd if=/dev/zero of=/dev/sdX bs=512 seek=<bad-block-number> count=1 > > you can test the block number to be really bad by > dd if=/dev/sdX of=/dev/null bs=512 skip=<bad-block-number> count=1 > if that command causes a input/output error, the block is bad. Yes, that cleared some errors, but unfortunately not all. That is one divice had 72bad blocks beforehand, and 44 afterwaeds, and the other had 9 beforehand, and 5 after. The second dd command actuallly did not report any bad blocks, but a selective badblocks command did. Anyway, is there something about Samsung disks not having spare blocks for this? > in fact, with each block, you have "lost" 512 bytes of data. your problem > is very simular to mine. > after overwriting the bad blocks, all should be fine again. > > you sould be able to "repair" all that bad blocks by a little xor'ing > script/program mentioned by neil brown. > if would be nice to have such a script where you can tell which > block/chunk is wrong and to which device to write to (and to read from). > with that program, the bad block will be overwritten with the (hopefully) > valid data and become functional again. yes, I still would like to find the inode in the raid file system from the bad block on a physical disk. > i also think this is a very common issue, that after a 1disk failue a 2nd > disk fails at resync because of bad blocks. > this could be prevented by doing a long smart check once a week or > something, but i did not had the idea to do that till today :) I will do some description of this on the wiki, in a while. Others may also contribute, you are most welcome to write something up for the wiki. > On Tue, 16 Feb 2010 06:38:41 +0200, Keld Simonsen <keld@xxxxxxxxxx> wrote: > > Further to my problems described below I dreamt up something that could > > solve my problem, till I got new disks installed. > > > > I am actually alive with a raid5 with 2 malfunctioning devices - > > something that is impossible... And I think I could be revived. > > And I think it is not an uncommon situation. > > > > I have badblocks. But only about 60 blocks on one drive and 10 on the > > other, out of 4 drives. It is an error rate of about 1 out of 20,000 > > or 99,995 % good data rate. If I could resync both the erroneous drives, > > and > > avoid the badblocks in the process, I would be safe (for some time). > > > > So if resync could be told to avoid the badblocks, and the file system > > in question also could be told to avoid the blocks then I could be in > > the air. I was then thinking of a userland resync process - no need to > > change the kernel, just install new mdadm and friends. Is that doable > > and useful? > > > > best regards > > keld > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
