Reconstructing RAID


Login or Register for Dates, Times and to Reply

 
Thread Tools Search this Thread
# 1  
Reconstructing RAID

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 -

Code:
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

Appreciate any assistance! Thanx!

Last edited by Neo; 11-21-2017 at 10:59 AM..
# 2  
From mdadm man:
Quote:
--examine applies to devices which are components
of an array, while --detail applies to a whole array which is currently active.
So you can --examine /dev/sdf4, for instance, not /dev/md2. And you can --detail /dev/md2, not /dev/sdf4. Smilie

Quote:
Also, the system can't seem to find the volume -
vgscan -v
Wait. We were speaking about a raid volume. This is for LVM(2) volumes: completely different things.

Quote:
Code:
mount -t auto dev/md2 /mnt/raid
mount: special device dev/md2 does not exist

Do you run it from the root directory? Otherwise dev/md2 is not /dev/md2.
--
Bye
This User Gave Thanks to Lem For This Post:
# 3  
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 -
Code:
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!
# 4  
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... Smilie

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)
Quote:
-f, --force
Assemble the array even if the metadata on some devices appears to be out-of-date.
If mdadm cannot find enough working devices to start the array, but can find some
devices that are recorded as having failed, then it will mark those devices as
working so that the array can be started. An array which requires --force to be
started may contain data corruption. Use it carefully.

-R, --run
Attempt to start the array even if fewer drives were given than were present last
time the array was active. Normally if not all the expected drives are found and
--scan is not used, then the array will be assembled but not started. With --run
an attempt will be made to start it anyway.
Let's made another attempt, manually inspecting the beginning of /dev/md2:

Code:
# 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
This User Gave Thanks to Lem For This Post:
# 5  
Doesn't look good. Here's a copy of what I see -
Code:
^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@

Takes up the whole screen.
# 6  
I guess it's hopeless then. I'll just have to wipe and re-use the disks. Thanx for all your help! Smilie
# 7  
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.
Login or Register for Dates, Times and to Reply

Previous Thread | Next Thread
Thread Tools Search this Thread
Search this Thread:
Advanced Search

Test Your Knowledge in Computers #735
Difficulty: Medium
The Commodore 64 was shipped with BASIC v2.0 in RAM.
True or False?

9 More Discussions You Might Find Interesting

1. Red Hat

RAID Configuration for IBM Serveraid-7k SCSI RAID Controller

Hello, I want to delete a RAID configuration an old server has. Since i haven't the chance to work with the specific raid controller in the past can you please help me how to perform the configuraiton? I downloaded IBM ServeRAID Support CD but i wasn't able to configure the video card so i... (0 Replies)
Discussion started by: @dagio
0 Replies

2. Solaris

Software RAID on top of Hardware RAID

Server Model: T5120 with 146G x4 disks. OS: Solaris 10 - installed on c1t0d0. Plan to use software raid (veritas volume mgr) on c1t2d0 disk. After format and label the disk, still not able to detect using vxdiskadm. Question: Should I remove the hardware raid on c1t2d0 first? My... (4 Replies)
Discussion started by: KhawHL
4 Replies

3. UNIX for Dummies Questions & Answers

Need help with RAID.

Hi Gurus, Can any one explain me the difference between hardware RAID and s/w RAID. Thanks in Advance. (1 Reply)
Discussion started by: rama krishna
1 Replies

4. AIX

SCSI PCI - X RAID Controller card RAID 5 AIX Disks disappeared

Hello, I have a scsi pci x raid controller card on which I had created a disk array of 3 disks when I type lspv ; I used to see 3 physical disks ( two local disks and one raid 5 disk ) suddenly the raid 5 disk array disappeared ; so the hardware engineer thought the problem was with SCSI... (0 Replies)
Discussion started by: filosophizer
0 Replies

5. Solaris

Creation of Raid 01 and Raid 10

Hello All, I have read enough of texts on Raid 01 and Raid 10 on solaris :wall: . But no-where found a way to create them using SVM. Some one pls tell me how to do or Post some link if that helps. TIA Curious solarister (1 Reply)
Discussion started by: Solarister
1 Replies

6. Solaris

implementing RAID 1 from RAID 5

Dear ALl, I have a RAID 5 volume which is as below d120 r 60GB c1t2d0s5 c1t3d0s5 c1t4d0s5 c1t5d0s5 d7 r 99GB c1t2d0s0 c1t3d0s0 c1t4d0s0 c1t5d0s0 d110 r 99GB c1t2d0s4 c1t3d0s4 c1t4d0s4 c1t5d0s4 d8 r 99GB c1t2d0s1 c1t3d0s1... (2 Replies)
Discussion started by: jegaraman
2 Replies

7. UNIX for Dummies Questions & Answers

RAID software vs hardware RAID

Hi Can someone tell me what are the differences between software and hardware raid ? thx for help. (2 Replies)
Discussion started by: presul
2 Replies

8. UNIX for Dummies Questions & Answers

regarding raid

Hello, I am aware that our system has two hard drives with raid but i'm not sure as to the type of raid the system uses. I tried this. # df Filesystem 512-blocks Free %Used Iused %Iused Mounted on /dev/hd4 229376 76272 67% 6748 12% / /dev/hd2 3080192... (1 Reply)
Discussion started by: h1timmboy
1 Replies

9. UNIX for Dummies Questions & Answers

reconstructing a record in a diffrent order

Can sed be used to take a existing record and reverse the order of defined character placement if there is no delimeters? existing record: 0123456789CO expected result: 9876543210CO if there were delimeters I could define the delimeter and each placement would have an id which I... (1 Reply)
Discussion started by: r1500
1 Replies

Featured Tech Videos