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Old 04-26-2011, 02:18 PM
Jussi Hirvi
 
Default mdraid woes (missing superblock?)

I have a raid1 array which is somehow faulty. There is 1,5 TB of stuff,
I would not want to lose it (though I have full backup).

The array cannot be mounted on startup (error message was "missing
superblock"). I had to boot from DVD with linux rescue and remove the
array from fstab.

Here is some info - I am a little dumbfounded.

[root@a134-224 log]# cat /proc/mdstat
(...)
md5 : active raid1 sdb1[0] sdd1[1]
1562505856 blocks [2/2] [UU]


## mdadm examine - I believe the following output indicates that there
really *is* a superblock

[root@a134-224 log]# mdadm --examine /dev/sdb1

/dev/sdb1:
Magic : a92b4efc
Version : 0.90.00
UUID : 194e7fdc:2a288e87:c03d8b24:c0120803
Creation Time : Sat Apr 23 20:41:08 2011
Raid Level : raid1
Used Dev Size : 1562505856 (1490.12 GiB 1600.01 GB)
Array Size : 1562505856 (1490.12 GiB 1600.01 GB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 5

Update Time : Tue Apr 26 11:48:35 2011
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Checksum : 657d7a24 - correct
Events : 14


Number Major Minor RaidDevice State
this 0 8 17 0 active sync /dev/sdb1

0 0 8 17 0 active sync /dev/sdb1
1 1 8 49 1 active sync /dev/sdd1


# examine the other partition/dev/sdd1:
Magic : a92b4efc
Version : 0.90.00
UUID : 194e7fdc:2a288e87:c03d8b24:c0120803
Creation Time : Sat Apr 23 20:41:08 2011
Raid Level : raid1
Used Dev Size : 1562505856 (1490.12 GiB 1600.01 GB)
Array Size : 1562505856 (1490.12 GiB 1600.01 GB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 5

Update Time : Tue Apr 26 11:48:35 2011
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Checksum : 657d7a46 - correct
Events : 14


Number Major Minor RaidDevice State
this 1 8 49 1 active sync /dev/sdd1

0 0 8 17 0 active sync /dev/sdb1
1 1 8 49 1 active sync /dev/sdd1



[root@a134-224 log]# mdadm --examine --scan
(...)
ARRAY /dev/md5 level=raid1 num-devices=2
UUID=194e7fdc:2a288e87:c03d8b24:c0120803


[root@a134-224 log]# mdadm --stop /dev/md5
mdadm: stopped /dev/md5

[root@a134-224 log]# mdadm --assemble /dev/md5
mdadm: /dev/md5 has been started with 2 drives.

# but it cannot be mounted:

[root@a134-224 log]# mount /dev/md5 /kvbck/
mount: you must specify the filesystem type
[root@a134-224 log]# mount -t ext3 /dev/md5 /kvbck/
mount: wrong fs type, bad option, bad superblock on /dev/md5,
missing codepage or other error
In some cases useful info is found in syslog - try
dmesg | tail or so

[root@a134-224 log]# tail /var/log/messages
Apr 26 17:14:09 localhost kernel: md: unbind<sdb1>
Apr 26 17:14:09 localhost kernel: md: export_rdev(sdb1)
Apr 26 17:14:09 localhost kernel: md: unbind<sdd1>
Apr 26 17:14:09 localhost kernel: md: export_rdev(sdd1)
Apr 26 17:14:17 localhost kernel: md: md5 stopped.
Apr 26 17:14:17 localhost kernel: md: bind<sdd1>
Apr 26 17:14:17 localhost kernel: md: bind<sdb1>
Apr 26 17:14:17 localhost kernel: raid1: raid set md5 active with 2 out
of 2 mirrors
Apr 26 17:14:56 localhost kernel: hfs: unable to find HFS+ superblock
Apr 26 17:15:05 localhost kernel: VFS: Can't find ext3 filesystem on dev
md5.

# Why does the log complain about HFS+ superblock? The fs should be ext3.

- Jussi

--
Jussi Hirvi * Green Spot
Suvilahdenkatu 1 B 78 * 00500 Helsinki * Finland
Tel. +358 9 493 981 * Mobile +358 40 771 2098 (only sms)
jussi.hirvi@greenspot.fi * http://www.greenspot.fi
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