I am trying to reconstruct a failed 4 disk RAID5 Western Digital ShareSpace device using 3 of the 4 disks connected via USB to an Ubuntu 12.04 machine. I get what seems like a successful re-assemble from -
mdadm --assemble --force /dev/md2 /dev/sde4 /dev/sdf4 /dev/sdg4
mdadm: /dev/md2 has been started with 3 drives (out of 4).
But then when I try to mount, it fails. I am logged in as root and when I try to troubleshoot with mdadm, I get odd returns such as -
mdadm --examine /dev/md2
mdadm: No md superblock detected on /dev/md2.
Also, the system can't seem to find the volume -
vgscan -v
Wiping cache of LVM-capable devices
Wiping internal VG cache
Reading all physical volumes. This may take a while...
Finding all volume groups
No volume groups found
I read in some other posts that the WD system uses LVM2. Could that be the issue? Here is the output from mdadm --detail
mdadm --detail /dev/md2
/dev/md2:
Version : 0.90
Creation Time : Mon Oct 19 10:26:15 2009
Raid Level : raid5
Array Size : 5854981248 (5583.75 GiB 5995.50 GB)
Used Dev Size : 1951660416 (1861.25 GiB 1998.50 GB)
Raid Devices : 4
Total Devices : 3
Preferred Minor : 2
Persistence : Superblock is persistent
Update Time : Sun Sep 2 15:22:50 2012
State : clean, degraded
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 64K
UUID : 4c4952ae:1477d756:234bdad8:bdaa1368
Events : 0.9246753
Number Major Minor RaidDevice State
0 8 84 0 active sync /dev/sdf4
1 8 68 1 active sync /dev/sde4
2 0 0 2 removed
3 8 100 3 active sync /dev/sdg4
Here's the result of the mount attempt-
mount -t auto dev/md2 /mnt/raid
mount: special device dev/md2 does not exist
That was a great catch! Although I was running it as root , I was NOT running the mount command from the root folder. Now when I run it -
mount -t auto /dev/md2 /mnt/raid I get -
mount: you must specify the filesystem type
I tried ext2, ext3 & ext4 but none seem to work. Any ideas?
mount -t ext3 /dev/md2 /mnt/raid
mount: wrong fs type, bad option, bad superblock on /dev/md2,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
mount -t ext2 /dev/md2 /mnt/raid
mount: wrong fs type, bad option, bad superblock on /dev/md2,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
mount -t ext4 /dev/md2 /mnt/raid
mount: wrong fs type, bad option, bad superblock on /dev/md2,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
I have been using the instructions from a post in the Western Digital Community forum -
"http://community.wdc.com/t5/WD-ShareSpace/HOWTO-Sharespace-RAID-5-Data-Recovery/td-p/287736"
The author admits that he's a Linux novice so would not know how to get past my problem, but this is where I got my info regarding the commands I documented. The output from dmesg | tail is -
[108585.149513] EXT3-fs (md2): error: can't find ext3 filesystem on dev md2.
[108585.161930] EXT4-fs (md2): VFS: Can't find ext4 filesystem
[108585.758247] ISOFS: Unable to identify CD-ROM format.
[108891.442375] EXT3-fs (md2): error: can't find ext3 filesystem on dev md2.
[108903.988734] EXT2-fs (md2): error: can't find an ext2 filesystem on dev md2.
[108915.586612] EXT4-fs (md2): VFS: Can't find ext4 filesystem
[109694.031696] EXT3-fs (md2): error: can't find ext3 filesystem on dev md2.
[109694.047559] EXT4-fs (md2): VFS: Can't find ext4 filesystem
[109694.653264] ISOFS: Unable to identify CD-ROM format.
[109694.671254] EXT2-fs (md2): error: can't find an ext2 filesystem on dev md2.
I have a bad feeling that there's something wrong with the partition tables. Appreciate your help!
From what I've been reading about those ShareSpace devices, there should be an LVM2 volume, indeed, on top of the raid. So you should find it, and then mount it. If things are like that, of course you cannot mount the raid volume itself, because it doesn't have a filesystem on it. But you didn't find the lvm2 volume, when running vgscan, so I don't have good feelings...
Since you've used --force to reassemble the raid (instead of only --run ), now the raid is active, but it could nonetheless be corrupted:
(from mdadm manual)
Let's made another attempt, manually inspecting the beginning of /dev/md2:
# dd if=/dev/md2 bs=512 count=255 skip=1 of=/tmp/md2lvm
# less /tmp/md2lvm
(Better than less, use a text editor of your choice).
Among binary data, do you see some LVM metadata declarations? Can you find the most recent one? Or there's nothing useful?
--
Bye
Without lvm metadata, I really don't know what could we do.
I'm sorry you didn't find someone more skilled than me. I'm neither a sysadmin nor an expert, actually.
Maybe you want to wait a little more for some help.
--
Bye.
