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Hello everyone, I am having an issue getting my mdadm raid 5 to mount. It seems like it has gotten a bad superblock or lost the filesystem somehow. This happened ...
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  1. #1
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    mdadm superblock mount issue


    Hello everyone,

    I am having an issue getting my mdadm raid 5 to mount. It seems like it has gotten a bad superblock or lost the filesystem somehow. This happened after a reboot, the raid was working before and I have about 1.8TB of data on it.

    Code:
    # fdisk -l
    
    Disk /dev/sda: 2000 GB, 2000396321280 bytes
    255 heads, 63 sectors/track, 243201 cylinders
    Units = cylinders of 16065 * 512 = 8225280 bytes
    
       Device Boot      Start         End      Blocks   Id  System
    /dev/sda1               1      243201  1953512001   fd  Lnx RAID auto
    
    Disk /dev/sdb: 2000 GB, 2000396321280 bytes
    255 heads, 63 sectors/track, 243201 cylinders
    Units = cylinders of 16065 * 512 = 8225280 bytes
    
       Device Boot      Start         End      Blocks   Id  System
    /dev/sdb1               1      243191  1953431676   fd  Lnx RAID auto
    Warning: Partition 1 does not end on cylinder boundary.
    
    Disk /dev/sdc: 2000 GB, 2000396321280 bytes
    255 heads, 63 sectors/track, 243201 cylinders
    Units = cylinders of 16065 * 512 = 8225280 bytes
    
       Device Boot      Start         End      Blocks   Id  System
    /dev/sdc1               1      243191  1953431676   fd  Lnx RAID auto
    Warning: Partition 1 does not end on cylinder boundary.
    
    Disk /dev/sdd: 8 GB, 8217054720 bytes
    255 heads, 63 sectors/track, 999 cylinders
    Units = cylinders of 16065 * 512 = 8225280 bytes
    
       Device Boot      Start         End      Blocks   Id  System
    /dev/sdd1   *           1        1000     8032468    b  FAT32
    Warning: Partition 1 does not end on cylinder boundary.
    Error: /dev/md127: unrecognised disk label
    Code:
    # cat /proc/mdstat
    Personalities : [raid6] [raid5] [raid4] [linear] [multipath] [raid0] [raid1] [raid10]
    md127 : active (auto-read-only) raid5 sdc1[3] sdb1[0] sda1[1]
          3906858624 blocks super 1.2 level 5, 64k chunk, algorithm 2 [3/3] [UUU]
    
    unused devices: <none>
    Code:
    # mdadm --detail /dev/md127
    /dev/md127:
            Version : 1.2
      Creation Time : Sun Sep  9 01:19:43 2012
         Raid Level : raid5
         Array Size : 3906858624 (3725.87 GiB 4000.62 GB)
      Used Dev Size : 1953429312 (1862.94 GiB 2000.31 GB)
       Raid Devices : 3
      Total Devices : 3
        Persistence : Superblock is persistent
    
        Update Time : Sun Sep  9 20:39:11 2012
              State : clean
     Active Devices : 3
    Working Devices : 3
     Failed Devices : 0
      Spare Devices : 0
    
             Layout : left-symmetric
         Chunk Size : 64K
    
               Name : ubuntu:1  (local to host ubuntu)
               UUID : c1d3dc22:591547b6:9f40b25e:7cd7a3d9
             Events : 26
    
        Number   Major   Minor   RaidDevice State
           0       8       17        0      active sync   /dev/sdb1
           1       8        1        1      active sync   /dev/sda1
           3       8       33        2      active sync   /dev/sdc1
    Code:
    # mount -t ext3 /dev/md127 4tb
    mount: wrong fs type, bad option, bad superblock on /dev/md127,
           missing codepage or helper program, or other error
           In some cases useful info is found in syslog - try
           dmesg | tail  or so
    Code:
    # dmesg | tail
    [   20.413469] ADDRCONF(NETDEV_UP): eth0: link is not ready
    [   21.862008] r8169 0000:02:00.0: eth0: link up
    [   21.868215] ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
    [   32.576026] eth0: no IPv6 routers present
    [ 8031.632455] EXT3-fs (md127): error: can't find ext3 filesystem on dev md127.
    [ 8031.652402] EXT4-fs (md127): VFS: Can't find ext4 filesystem
    [ 8031.672284] FAT-fs (md127): bogus number of FAT structure
    [ 8031.672290] FAT-fs (md127): Can't find a valid FAT filesystem
    [ 8031.696268] SQUASHFS error: Can't find a SQUASHFS superblock on md127
    [ 8040.053649] EXT3-fs (md127): error: can't find ext3 filesystem on dev md127.
    Please let me know if you have any solutions. I would like to be able to retrieve the data. If there is a way to somehow copy the data to a spare disk let me know.

    Thanks for any help that you may have.

  2. #2
    Linux Engineer Kloschüssel's Avatar
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    Are you sure there is no LVM container around your partition stored across the harddrives? The raid seems to be functioning properly.

  3. #3
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    Thanks for the reply. I am sure there is no LVM. I ran these just to be sure:

    Code:
    # pvscan
      No matching physical volumes found
    # pvdisplay
    # lvm pvs
    So there is no LVM.

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  5. #4
    Linux Engineer Kloschüssel's Avatar
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    If you know that the filesystem should be ext3 (or at least ext2) and the first superblock is broken you can try to get to a backup superblock which ext2+3 creates by itself. How is described here:

    Advanced Find ext2 ext3 Backup SuperBlock - CGSecurity

    Beware from running fsck on a non-ext partition!! It will erase your data! The safest thing to do would be to dry-run the commands on a backup. If things go well, you could then run the same command on the original data and restore the partitions.

    Anyway, it seems odd to me that a superblock is broken on a RAID 5. This should NEVER happen unless there is a hardware malfunction across more than one physical hard drive! Did the RAID fail sometime ago claiming that a disk is broken?

    Good luck!

  6. #5
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    I tried to run the testdisk program on /dev/md127. It found a filesystem but was not able to do anything with it. It said it was not able to repair it or do anything to it such as list the superblocks.

    As far as I know the raid never failed. It was working fine and then it stopped working after a reboot.

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