On Wed, 16 Oct 2013 22:27:54 -0400 peter@xxxxxxxxxxxx wrote: > Thanks Neil, > > I've checked the drives and sdd had unrecoverable read errors which > was the reason that the rebuilding of sdh failed in the first place. > > Then I made a clone of sdd with ddrescue and it looks like only 4096 > bytes was completely unreadable. > > Then I did the --force assemble as you suggested using the 3 good > drives and the cloned sdd. I ran e2fsck after that and temporarily > mounted the array to check that it looked OK. > > Now I've added sdh again and the rebuilding process is underway. > Hopefully it will complete. > > > I was just wondering but since I lost 4kB of data when I cloned sdd, > does that mean that I will have 4x4kB of garbled data somewhere since > I assembled 4 drives (n-1) and the raid system wouldn't know? Or would > that have been detected somehow when I ran fsck (ext3)? You could have 2*4kB of garbled data (the block you lost, and the corresponding block on the device that was rebuilt). Or you could have 1*4kB, or 0*4kB garbled if either the corrupted block or the recovered block were parity blocks. Those bad blocks are not likely in filesystem metadata else fsck should have noticed. They could be in some file(s), or in some free space - in which case you'll never notice. NeilBrown
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