On Fri, 12 Feb 2010 01:24:30 +0100 Michael <michael@xxxxxxx> wrote: > Hello, > > i've came into the situation that one of my 4 mdadm raid5 drives failed. > not realy faild, but not detectet at system startup. so i started resync, > and one of the remaining hdd's had a bad block and faild. so 2 drives > offline and raid not functional anymore. > > 1st question: > i have read that it is possible with debugfs to locate which file belongs > to the bad block on a ext file system. good thing, so i can check if i have > *lost* an inportant or an unimportant file... or just free space. > problen with this is, that i cant map the known bad block from, lets say, > sda to my raid array md0. > > is there any method to find that bad block in context of the raid block > device? reading all files is not a good option on large raidsets. > level 5, 64k chunk, algorithm 2 It isn't that hard. The code is in drivers/md/raid5.c in the kernel..... Rather than trying to describe in general, give me the block number, device, and "mdadm --examine" of that device, and I'll tell you how I get the answer. > > 2nd question: > > in my case, i have a functional raid5 array with 3 of 4 disks, in which > one of the active discs has a bad sector. assume that the one failed disk > has consistent parity information/data on this sector, but has been altered > so that a complete resync would not work. is there a way to resync only > that one chunk that belongs to the block? using the data from the 3 drives > without a bad block, even if one is not a active part of the array but was > before? No. If you were desperate, you could use 'dd' to read each of the chunks into a file, then write a little c/perl/whatever program to xor those files together, then use 'dd' to write that file back out the the target chunk. NeilBrown -- 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
