RAID5 - can't mount /dev/md0

[Gustavo Melo]

Hi,

I hope someone can help me with this, as I already read all I could find about RAID 5 and nothing...

I had a Fedora 7 file server consisting of a 20GB drive containing the OS and a 3 160GB drives RAID 5 array containing the user's data.

Last week the 20GB drive failed, so I replaced it with a fedora 8 drive from another install, booted and tried to start the RAID array, which happened without errors.

I can't, however, mount the /dev/md0 partition:

# mount /dev/md0 /files
mount: wrong fs type, bad option, bad superblock on /dev/md0,
       missing codepage or helper program, or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

# dmesg | tail
EXT3-fs error (device md0): ext3_check_descriptors: Block bitmap for group 0 not in group (block 32800)!
EXT3-fs: group descriptors corrupted!

The data in this array is VERY IMPORTANT, so I'm don't want to make anything stupid..

Can any of you help me with this?

Thanks in advance,

Gustavo Melo

[savage]

See what

mdadm --detail /dev/md0

says, it should give you some output telling you the status of the raid array.

If all looks good in there, check it's still partitioned properly with fdisk (don't make any changes if it's critical data).

You can try running fsck on it too.

[Gustavo Melo]

Thank you for your response; Here's the result:

# mdadm --detail /dev/md0
/dev/md0:
        Version : 00.90.03
  Creation Time : Wed Jun 25 12:16:52 2008
     Raid Level : raid5
     Array Size : 320159104 (305.33 GiB 327.84 GB)
  Used Dev Size : 160079552 (152.66 GiB 163.92 GB)
   Raid Devices : 3
  Total Devices : 3
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Thu Jul  3 09:17:04 2008
          State : clean
 Active Devices : 3
Working Devices : 3
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 4K

           UUID : 501b2b54:bca6cd20:d084dc4b:f63efc2d
         Events : 0.182

    Number   Major   Minor   RaidDevice State
       0       8       17        0      active sync   /dev/sdb1
       1       8       33        1      active sync   /dev/sdc1
       2       8       49        2      active sync   /dev/sdd1

fsck -n /dev/md0
fsck 1.40.4 (31-Dec-2007)
e2fsck 1.40.4 (31-Dec-2007)
fsck.ext3: Group descriptors look bad... trying backup blocks...
fsck.ext3: Bad magic number in super-block while trying to open /dev/md0

The superblock could not be read or does not describe a correct ext2
filesystem.  If the device is valid and it really contains an ext2
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
    e2fsck -b 8193 <device>

# fdisk -l

Disk /dev/sda: 20.0 GB, 20020396032 bytes
255 heads, 63 sectors/track, 2434 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0xa042a042

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          25      200781   83  Linux
/dev/sda2              26        2434    19350292+  8e  Linux LVM

Disk /dev/sdb: 163.9 GB, 163928604672 bytes
255 heads, 63 sectors/track, 19929 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x0005d952

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1       19929   160079661   fd  Linux raid autodetect

Disk /dev/sdc: 163.9 GB, 163928604672 bytes
255 heads, 63 sectors/track, 19929 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x000c8502

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1               1       19929   160079661   fd  Linux raid autodetect

Disk /dev/sdd: 163.9 GB, 163928604672 bytes
255 heads, 63 sectors/track, 19929 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x000404e2

   Device Boot      Start         End      Blocks   Id  System
/dev/sdd1               1       19929   160079661   fd  Linux raid autodetect

Disk /dev/dm-0: 19.2 GB, 19226689536 bytes
255 heads, 63 sectors/track, 2337 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00000000

Disk /dev/dm-0 doesn't contain a valid partition table

Disk /dev/dm-1: 536 MB, 536870912 bytes
255 heads, 63 sectors/track, 65 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x30307800

Disk /dev/dm-1 doesn't contain a valid partition table

Disk /dev/md0: 327.8 GB, 327842922496 bytes
2 heads, 4 sectors/track, 80039776 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Disk identifier: 0x0e6b04eb

    Device Boot      Start         End      Blocks   Id  System