How to mount parition in from a working driver in RAID1

Question

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

Solution

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.

Comments

[Danila Ladner]

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?

[ProDraz]

@DanilaLadner I've updated my original post, was misstype, mounting md127 works, but as said It doesn't reveal more then 100mb of data and that's some grub files, I guess that's because it's boot partition or something.

[Danila Ladner]

can you show what mdadm --examine --scan shows? and what mdadm --detail /dev/md126 show?

[Danila Ladner]

oh sorry then. what about mdadm --detail /dev/md1 and /dev/md2

[ProDraz]

@DanilaLadner updated OP (at bottom)

[Danila Ladner]

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.

[ProDraz]

@DanilaLadner check OP again :S

[Danila Ladner]

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

[c2h5oh]

try mdadm --assemble --scan and if it succeeds try mounting /dev/md1

[ProDraz]

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

[Michael Hampton]

Yep, looks like they were RAID 0 and you lose. Sorry. Hope you had good backups.