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#1 2017-08-12 12:42:45

luusac
Member
Registered: 2008-04-29
Posts: 356

raid failure/bitmap/group desciptors corruption

Hi,
After storing a few gb on my dns-323 last night, waiting until transfers had stopped and shutting down the box via the web interface (as far as I remember it did it via the web and not the button - memory us fuzzy it was rather late) I turn on the box this morning to be prompted to set up raid (wizard).  I can't telnet or ssh into the box with ffp anymore.  I have pulled one of the drives, put it in a usb caddy (using laptop) and tried to connect via ubuntu using:

mount -o ro -t ext2 /dev/md0 /tmp/mountpoint

after that got me nowhere I installed mdadm and tried

sudo mdadm --assemble /dev/md0 /dev/sdc2 --run
mdadm: /dev/md0 has been started with 1 drive (out of 2).

sudo mdadm --detail /dev/md0
/dev/md0:
        Version : 0.90
  Creation Time : Fri Aug 22 01:41:48 2008
     Raid Level : raid1
     Array Size : 974133312 (929.01 GiB 997.51 GB)
  Used Dev Size : 974133312 (929.01 GiB 997.51 GB)
   Raid Devices : 2
  Total Devices : 1
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Sat Aug 12 10:07:55 2017
          State : clean, degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 0
  Spare Devices : 0

           UUID : 0c391687:af39f816:d362f0bc:fac566aa
         Events : 0.2756281

    Number   Major   Minor   RaidDevice State
       0       8       34        0      active sync   /dev/sdc2
       2       0        0        2      removed

dmesg:
[ 4999.902192] md: bind<sdc2>
[ 4999.904887] md/raid1:md0: active with 1 out of 2 mirrors
[ 4999.904948] md0: detected capacity change from 0 to 997512511488

[ 5112.362546] EXT4-fs (md0): mounting ext2 file system using the ext4 subsystem
[ 5112.382698] EXT4-fs (md0): ext4_check_descriptors: Block bitmap for group 3968 not in group (block 384067452)!
[ 5112.382700] EXT4-fs (md0): group descriptors corrupted!

When I click on the 998GB volume in nautilus I get:
Error mounting /dev/md0 at /media/houthalen/e175b8b4-c01e-434d-b90e-754a8bfcb549: Command-line `mount -t "ext2" -o "uhelper=udisks2,nodev,nosuid" "/dev/md0" "/media/houthalen/e175b8b4-c01e-434d-b90e-754a8bfcb549"' exited with non-zero exit status 32: mount: wrong fs type, bad option, bad superblock on /dev/md0,
       missing codepage or helper program, or other error

I relise the fs type is ext2, so I don't understand why the "mounting ext2 file system using the ext4 subsystem".

I have pulled both drives from the DNS-323 (one at a time and returned them to their original bays so I don't get mixed up with left/right drives) and get the same results.

I have another drive that I can copy everything to, but want to take the least destructive method of getting access to the raid partition.  Can anybody help me further?
Thanks

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#2 2017-08-13 16:23:20

Mijzelf
Member / Developer
Registered: 2008-07-05
Posts: 689

Re: raid failure/bitmap/group desciptors corruption

I relise the fs type is ext2, so I don't understand why the "mounting ext2 file system using the ext4 subsystem".

In newer Linux kernels the ext4 driver is also used for mounting ext2 and -3 filesystems. I guess this is done to ease the code maintenance.

It looks like the filesystem is corrupted. Maybe you had a power failure when shutting down the NAS?

You can try to run fsck on the md volume. (Don't try on both disks. If it fails on one, it won't succeed on the other). *Maybe* it will help to install the ext2 kernel module, and try to mount using that fs driver.

(one at a time and returned them to their original bays so I don't get mixed up with left/right drives)

That shouldn't matter. The raid header contains all information needed to assemble the array. The physical location is not important.

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