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One of hard drives in array is dead, I'm unsure if it's raid0 or raid1, what I'm trying to achieve is mount the working drive and make a backup of what's left.

If I mount /dev/md127 then I can see only some grub files, total size it arround 100mb.

If I try to mount /dev/md1 I get:

root@rescue:~# mount /dev/md1 /mnt
mount: /dev/md1: can't read superblock

Some outputs:

root@rescue:~# fdisk -l
Disk /dev/sdb: 1500.3 GB, 1500301910016 bytes
255 heads, 63 sectors/track, 182401 cylinders, total 2930277168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0001f015

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *          63      208844      104391   fd  Linux raid autodetect
/dev/sdb2          208845    16787924     8289540   fd  Linux raid autodetect
/dev/sdb3        16787925  2930272064  1456742070   fd  Linux raid autodetect

Disk /dev/md127: 106 MB, 106823680 bytes
2 heads, 4 sectors/track, 26080 cylinders, total 208640 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/md127 doesn't contain a valid partition table


root@rescue:~# cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] [multipath] [faulty]
md127 : active raid1 sdb1[1]
      104320 blocks [2/1] [_U]

unused devices: <none>

   root@rescue:~# mdadm --examine /dev/sdb2
/dev/sdb2:
          Magic : a92b4efc
        Version : 0.90.00
           UUID : fca66a1e:c6aba1f7:ace437e0:ae545265
  Creation Time : Thu Oct 21 01:57:07 2010
     Raid Level : raid0
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 1

    Update Time : Thu Oct 21 01:57:07 2010
          State : active
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0
       Checksum : 6138e9b8 - correct
         Events : 1

     Chunk Size : 256K

      Number   Major   Minor   RaidDevice State
this     1       8       18        1      active sync   /dev/sdb2

   0     0       8        2        0      active sync
   1     1       8       18        1      active sync   /dev/sdb2

If anyone could share, how to mount driver properly to be able to access data (preferably in read-only mode so I don't mess up anything if that's possible)...

root@rescue:~# mdadm --examine --scan
ARRAY /dev/md127 UUID=0464b5c4:d777ef5e:17b64c46:2e5e61c3
ARRAY /dev/md1 UUID=fca66a1e:c6aba1f7:ace437e0:ae545265
ARRAY /dev/md2 UUID=46c22b6d:dc9668a4:13d0e329:c7b8b0ca

AND

root@rescue:~# mdadm --detail /dev/md126
mdadm: cannot open /dev/md126: No such file or directory

AND

root@rescue:~/dd_rescue# mdadm --detail /dev/md1
mdadm: md device /dev/md1 does not appear to be active.
root@rescue:~/dd_rescue#
root@rescue:~/dd_rescue#
root@rescue:~/dd_rescue#
root@rescue:~/dd_rescue# mdadm --detail /dev/md2
mdadm: md device /dev/md2 does not appear to be active.

SMART

    root@rescue:~# smartctl -a /dev/sda
smartctl 5.41 2011-06-09 r3365 [i686-linux-3.2.2-xxxx-std-ipv6-32] (local build)
Copyright (C) 2002-11 by Bruce Allen, http://smartmontools.sourceforge.net

=== START OF INFORMATION SECTION ===
Device Model:     ST_M13FQBL
Serial Number:    QNR_BFW
Firmware Version: 1117F38F
User Capacity:    4,142,054,400 bytes [4.14 GB]
Sector Size:      512 bytes logical/physical
Device is:        Not in smartctl database [for details use: -P showall]
ATA Version is:   6
ATA Standard is:  ATA/ATAPI-6 T13 1410D revision 2
Local Time is:    Thu May 16 01:37:37 2013 CEST
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

Error SMART Values Read failed: scsi error aborted command
Smartctl: SMART Read Values failed.

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: UNKNOWN!
SMART Status, Attributes and Thresholds cannot be read.

Error SMART Error Log Read failed: scsi error aborted command
Smartctl: SMART Error Log Read Failed
Error SMART Error Self-Test Log Read failed: scsi error aborted command
Smartctl: SMART Self Test Log Read Failed
Device does not support Selective Self Tests/Logging
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1  
Why are you trying to mount /dev/md1? your /boot partition is on /dev/md127 seems like. In /dev/ path do you see only /dev/md127? –  Danila Ladner May 15 '13 at 20:54
1  
can you show what mdadm --examine --scan shows? and what mdadm --detail /dev/md126 show? –  Danila Ladner May 15 '13 at 21:06
1  
oh sorry then. what about mdadm --detail /dev/md1 and /dev/md2 –  Danila Ladner May 15 '13 at 21:11
1  
Ok. so you need to see why that drive did not show up. Is this a VM? any smart errors detected? Some more info need for that drive, if it is completely dead, you are screwed with that dead drive raid0 config. –  Danila Ladner May 15 '13 at 22:50
1  
Well yeah it cannot read any smart errors, that means the disk is shut along with its s.m.a.r.t output on the controller of the disk. I hope you have backups. + Try never ever create something with raid0 in production, if raid0 is stuck in your head as best solution then, at least mirror it --> raid 0+1 –  Danila Ladner May 16 '13 at 2:49

2 Answers 2

up vote 2 down vote accepted

With one of the drives dead you will no longer be able to mount /dev/md1 - you have to mount a partition on the drive that is still alive: /dev/sdb2 or /dev/sdb3

You can get more information using mdadm --examine /dev/sdb2

If sdb2 and sdb3 were running RAID0 all data on those partitions is lost.

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Doesn't work... root@rescue:~# mount /dev/sdb3 /mnt mount: unknown filesystem type 'linux_raid_member'. Also there is output of mdadm --examine /dev/sdb2 in OP, I guess I've lost all data :S –  ProDraz May 15 '13 at 21:04
    
try mdadm --assemble --scan and if it succeeds try mounting /dev/md1 –  c2h5oh May 15 '13 at 21:09
    
root@rescue:~/dd_rescue# mdadm --assemble --scan mdadm: /dev/md/2_0 assembled from 1 drive - not enough to start the array. mdadm: /dev/md/1_0 assembled from 1 drive - not enough to start the array. mdadm: No arrays found in config file or automatically –  ProDraz May 15 '13 at 22:27
    
Yep, looks like they were RAID 0 and you lose. Sorry. Hope you had good backups. –  Michael Hampton May 15 '13 at 22:33

You have to specify the filesystem type when mounting a partition, like

mount -o ro -t ext3 /dev/sdb2 /mnt

if you know its ext3. ro - for mounting readonly.

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