Hi, Thanks Andreas, Yes apparently, 3/4 of the original disks seem to be safe. But I'm terrified at the idea of doing something wrong assembling them. Incidentally, I indeed did a mistake trying to assemble the ddrescue images of the 3 safe disks. I tried to create again with proper metadata and chunck but it did not work. I'm still scared at the idea of restarting the original raid. I'm currently ddrescuing again the 3 partitions to then try and *assemble* them rather than *create*. Thanks Wol, I use loop devices because I work on partition images, not on actual partitions: I use ddrescue to copy data from /dev/sd[abc]10 to some.other.server:/home/sd[abc].img Then I go to some.other.server and turn the images into loop devices : losetup /dev/loop0 /home/sda10.img losetup /dev/loop1 /home/sdb10.img losetup /dev/loop2 /home/sdc10.img Then I tried to created the raid, it worked but as I said, the filesystem was unreadable. I know the idea of using loop devices works because I tested it before. I'm doing the whole procedure all over again (takes 5 days to ddrescue the 3 partitions to another server) and then I will use the command you recommended : mdadm --assemble /dev/md0 /dev/loop0 /dev/loop1 /dev/loop2 --force Will keep you posted ------------------------- Santiago DIEZ Quark Systems & CAOBA 23 rue du Buisson Saint-Louis, 75010 Paris ------------------------- On Mon, Oct 10, 2016 at 12:39 AM, Wols Lists <antlists@xxxxxxxxxxxxxxx> wrote: > > On 08/10/16 13:30, Andreas Klauer wrote: > > On Fri, Oct 07, 2016 at 05:37:32PM +0200, Santiago DIEZ wrote: > >> > First thing I did is ddrescue the remaining partitions sd[abc]10 . > >> > ddrescue did not stumble into any read error so I assume all remaining > >> > partitions are perfectly safe. > > So ... don't you still have a good copy? > > > > You only killed one of them, right? Did not make same mistake twice? > > > >> > There comes my mistake: I ran the --create command instead of --assemble : > >> > > >> > ================================================================================ > >> > # mdadm --create --verbose /dev/md1 --raid-devices=4 --level=raid5 > >> > --run --readonly /dev/loop0 /dev/loop1 /dev/loop2 missing > > One oddity I've noticed. You've created the array using loop devices. > What are these? > > The reason I ask is that using loopback devices is a standard technique > for rebuilding a damaged array, specifically to prevent md from actually > writing to the drive. So is it possible that "mdadm --create" only wrote > to ram, and a reboot will recover your ddrescue copies untouched? > > My raid-fu isn't enough to tell me whether I'm right or not ... :-) > > If necessary you'll have to do another ddrescue from the original > drives, and you should then be able to assemble the array from the > copies. Don't use "missing", use "--force" and you should get a working, > degraded, array to which you can add a new drive and rebuild the array. > > mdadm --assemble /dev/md0 /dev/sd[efg]10 --force > > if I'm right ... so long as it's the copies, you can always recover > again from the original disks, and if there's a problem with the copies > mdadm should complain when it assembles the array. > > Cheers, > Wol -- 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
