mdadm: no md superblock
So I seriously screwed up. I am reinstalling gentoo on my system and during the install I tried to create my software raid using the following:
(DONT USE THIS) mdadm --assemble /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1 the correct syntax would have been: mdadm --assemble /dev/md0 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1 which now tells me that one or more drives is missing its superblock which is of course is the WRONG syntax. I then proceeded to run that same command with different drives at the front of the list, which appears to erased the superblocks on all my drives. The last time I ran examine I got the following: /dev/sdc1: Magic : a92b4efc Version : 00.90.00 UUID : c362e3fb:514a460d:26f3c1cd:393ff9ac Creation Time : Thu Oct 18 05:18:43 2007 Raid Level : raid5 Used Dev Size : 488383488 (465.76 GiB 500.10 GB) Array Size : 1465150464 (1397.28 GiB 1500.31 GB) Raid Devices : 4 Total Devices : 4 Preferred Minor : 0 Update Time : Thu Jul 31 15:54:06 2008 State : clean Active Devices : 4 Working Devices : 4 Failed Devices : 0 Spare Devices : 0 Checksum : caeb45fd - correct Events : 0.331696 Layout : left-symmetric Chunk Size : 1024K Number Major Minor RaidDevice State this 2 8 33 2 active sync /dev/sdc1 0 0 8 1 0 active sync 1 1 8 49 1 active sync 2 2 8 33 2 active sync /dev/sdc1 3 3 8 17 3 active sync Of course now running mdadm -E /dev/sdc1 returns mdadm: No md superblock detected on /dev/sdc1. Same for all the others. Is there a way to recreate the superblocks with this information? I know there are other postings similiar to this, but considering this is loads of my data I would sort of like assurance that I won't screw things up (more). |
Erggh - I did that once, but only to one of my drives fortunately, allowing me to rebuild.
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So I found this: http://kev.coolcavemen.com/2007/03/h...d-superblocks/
but when I when I run: mdadm --create /dev/md0 --chunk=1024 --verbose --level=5 --raid-devices=4 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1 I get: mdadm: layout defaults to left-symmetric mdadm: /dev/sda1 is too small: 0K mdadm: /dev/sdb1 is too small: 0K mdadm: /dev/sdc1 is too small: 0K mdadm: /dev/sdd1 is too small: 0K mdadm: create aborted Any idea on that? |
Unfortunately, the only solution I know of is to rebuild the whole shooting match from backup.
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Hmm, I think the file descriptors are just messed up. For instance any attempts to access the sda1/b1/c1/d1 device files results in unable to read. Obviously I wouldn't actually want to fdisk /dev/sda1 but it should open the tool at least when I try to. Instead I get:
livecd gentoo # fdisk /dev/sda1 Unable to read /dev/sda1 We'll see what happens when I reboot (after I finish the gentoo install). |
oops
So turns out I didn't erase the superblocks, I just destroyed the device files in /dev. If I had erased the superblock then the create method above would have fixed it, instead a reboot did the trick.
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That's good to know; I'll try to remember that next time I forget the /dev/md0...
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