Persistent superblock error

Saurabh Barve <sa@xxxxxxxxxxxxxxxxxxx> · Thu, 21 Oct 2004 16:54:32 -0600

Hi,

I recently lost 2 hard drives in my 4-drive RAID-5 array. I replaced the 
two faulty hard drives and tried rebuilding the array. However, I 
continue to get errors.

I created the raid array using madam:

mdadm --assemble /dev/md0 --update=summaries /dev/hdc1 /dev/hdd1 
/dev/hdg1 /dev/hdh1

I then tried to run fsck on /dev/md0 to make sure there were no file 
system errors. However, fsck returned error messages that the number of 
cylinders according to the superblock were 183833712, while the physical 
size of the device was 183104736.

Running fdisk on /dev/md0 returned the following:

--------------

Device contains neither a valid DOS partition table, nor Sun, SGI or OSF 
disklabel

Building a new DOS disklabel. Changes will remain in memory only,

until you decide to write them. After that, of course, the previous

content won't be recoverable.

The number of cylinders for this disk is set to 183104736.

There is nothing wrong with that, but this is larger than 1024,

and could in certain setups cause problems with:

1) software that runs at boot time (e.g., old versions of LILO)

2) booting and partitioning software from other OSs

   (e.g., DOS FDISK, OS/2 FDISK)

Warning: invalid flag 0x0000 of partition table 4 will be corrected by 
w(rite)

Command (m for help): p

Disk /dev/md0: 749.9 GB, 749996998656 bytes
2 heads, 4 sectors/track, 183104736 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
---------------

I tried inspecting the raid array with mdamd - 'mdadm --detail --test 
/dev/md0'. It gave me the following results:

------------------

/dev/md0:

        Version : 00.90.00

  Creation Time : Thu Oct 21 16:27:20 2004

     Raid Level : raid5

     Array Size : 732418944 (698.49 GiB 749.100 GB)

    Device Size : 244139648 (232.83 GiB 249.100 GB)

   Raid Devices : 4

  Total Devices : 4

Preferred Minor : 0

    Persistence : Superblock is persistent

    Update Time : Thu Oct 21 16:38:59 2004
          State : dirty, degraded
 Active Devices : 2
Working Devices : 3
 Failed Devices : 1
  Spare Devices : 1

         Layout : left-symmetric
     Chunk Size : 64K

           UUID : c7a73d47:a072c630:7693d236:dff40ca6
         Events : 0.6

    Number   Major   Minor   RaidDevice State
       0      22        1        0      active sync   /dev/hdc1
       1      22       65        1      faulty   /dev/hdd1
       2       0        0        2      faulty removed
       3      34       65        3      active sync   /dev/hdh1

       4      34        1        4      spare   /dev/hdg1
--------------------

My /etc/raidtab files reads like this:

---------
raiddev /dev/md0
        raid-level              5
        nr-raid-disks           4
        nr-spare-disks          0
        persistent-superblock   1
        parity-algorithm        left-symmetric
        chunk-size              64
        device                  /dev/hdc1
        raid-disk               0
        device                  /dev/hdd1
        raid-disk               1
        device                  /dev/hdg1
        raid-disk               2
        device                  /dev/hdh1
        raid-disk               3
----------

Any advice on why my RAID array will not run?

Thanks,
Saurabh.
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