Re: Can't mount /dev/md0 Raid5

[NeilBrown <neilb@suse.com>]

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On Wed, Oct 11 2017, Joseba Ibarra wrote:

> Hi Mikael,
>
> I had ext4
>
> and for commands:
>
> root@grafico:/mnt# fsck -n /dev/md0
> fsck de util-linux 2.29.2
> e2fsck 1.43.4 (31-Jan-2017)
> ext2fs_open2(): Bad magic number in superblock
> fsck.ext2: invalid superblock, trying backup blocks...
> fsck.ext2: Bad magic number in super-block while trying to open /dev/md0
>
> The superblock could not be read or does not describe a ext2/ext3/ext4 
> filesystem.
> If the device is invalid and it really contains an ext2/ext3/ext4 filesystem
> (and not swap or ufs or something else), then the superblock is corrupt; 
> and you might try running e2fsck with an alternate superblock:
>      e2fsck -b 8193 <device>
>   o
>      e2fsck -b 32768 <device>
>
> A gpt partition table is found in /dev/md0


Mikael suggested:

>> try to run fsck -n (read-only) on md0 and/or md0p1.

But you only tried
   fsck -n /dev/md0
why didn't you also try
   fsck -n /dev/md0p1
??

NeilBrown


>
>
> I'm getting more escared....... No idea what to do
>
> Thanks
>> Mikael Abrahamsson <mailto:swmike@swm.pp.se>
>> 11 de octubre de 2017, 16:01
>> On Wed, 11 Oct 2017, Joseba Ibarra wrote:
>>
>>
>> Do you know what file system you had? Looks like next step is to try 
>> to run fsck -n (read-only) on md0 and/or md0p1.
>>
>> What does /etc/fstab contain regarding md0?
>>
>> Joseba Ibarra <mailto:wajalotnet@gmail.com>
>> 11 de octubre de 2017, 13:56
>> Hi Adam
>>
>> root@grafico:/mnt# cat /proc/mdstat
>> Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] 
>> [raid4] [raid10]
>> md0 : inactive sdd1[3] sdb1[1] sdc1[2]
>>       2929889280 blocks super 1.2
>>
>> unused devices: <none>
>>
>>
>> root@grafico:/mnt# mdadm --manage /dev/md0 --stop
>> mdadm: stopped /dev/md0
>>
>>
>> root@grafico:/mnt# mdadm --assemble /dev/md0 /dev/sd[bcd]1
>> mdadm: /dev/md0 assembled from 3 drives - not enough to start the 
>> array while not clean - consider --force.
>>
>>
>>
>> root@grafico:/mnt# cat /proc/mdstat
>> Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] 
>> [raid4] [raid10]
>> unused devices: <none>
>>
>> At this point I´ve followed the advise using --force
>>
>> root@grafico:/mnt# mdadm --assemble --force /dev/md0 /dev/sd[bcd]1
>> mdadm: Marking array /dev/md0 as 'clean'
>> mdadm: /dev/md0 has been started with 3 drives (out of 4).
>>
>>
>> root@grafico:/mnt# cat /proc/mdstat
>> Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] 
>> [raid4] [raid10]
>> md0 : active (auto-read-only) raid5 sdb1[1] sdd1[3] sdc1[2]
>>       2929889280 blocks super 1.2 level 5, 512k chunk, algorithm 2 
>> [4/3] [_UUU]
>>       bitmap: 0/8 pages [0KB], 65536KB chunk
>>
>> unused devices: <none>
>>
>>
>> Now I see the RAID, however can't be mounted. So, I'm not sure how to 
>> backup the data. Gparted shows the partition /dev/md0p1 with the used 
>> and free space.
>>
>>
>> If I try
>>
>> mount /dev/md0 /mnt
>>
>> again the output is
>>
>> mount: wrong file system, bad option, bad superblock in /dev/md0, 
>> missing codepage or helper program, or other error
>>
>>     In some cases useful info is found in syslog - try dmesg | tail or 
>> something like that.
>>
>> I do dmesg | tail
>>
>> If I try root@grafico:/mnt# mount /dev/md0p1 /mnt
>> mount: /dev/md0p1: can't read superblock
>>
>> And
>>
>>
>> root@grafico:/mnt# dmesg | tail
>> [ 3263.411724] VFS: Dirty inode writeback failed for block device 
>> md0p1 (err=-5).
>> [ 3280.486813]  md0: p1
>> [ 3280.514024]  md0: p1
>> [ 3452.496811] UDF-fs: warning (device md0): udf_fill_super: No 
>> partition found (2)
>> [ 3463.731052] JBD2: Invalid checksum recovering block 630194476 in log
>> [ 3464.933960] Buffer I/O error on dev md0p1, logical block 630194474, 
>> lost async page write
>> [ 3464.933971] Buffer I/O error on dev md0p1, logical block 630194475, 
>> lost async page write
>> [ 3465.928066] JBD2: recovery failed
>> [ 3465.928070] EXT4-fs (md0p1): error loading journal
>> [ 3465.936852] VFS: Dirty inode writeback failed for block device 
>> md0p1 (err=-5).
>>
>>
>> Thanks a lot for your time
>>
>>
>> Joseba Ibarra
>>
>> Adam Goryachev <mailto:adam@websitemanagers.com.au>
>> 11 de octubre de 2017, 13:29
>> Hi Rudy,
>>
>> Please send the output of all of the following commands:
>>
>> cat /proc/mdstat
>>
>> mdadm --manage /dev/md0 --stop
>>
>> mdadm --assemble /dev/md0 /dev/sd[bcd]1
>>
>> cat /proc/mdstat
>>
>> mdadm --manage /dev/md0 --run
>>
>> mdadm --manage /dev/md0 --readwrite
>>
>> cat /proc/mdstat
>>
>>
>> Basically the above is just looking at what the system has done 
>> currently, stopping/clearing that, and then trying to assemble it 
>> again, finally, we try to start it, even if it has one faulty disk.
>>
>> At this stage, chances look good for recovering all your data, though 
>> I would advise to get yourself a replacement disk for the dead one so 
>> that you can restore redundancy as soon as possible.
>>
>> Regards,Adam
>>
>>
>>
>>
>>
>> Joseba Ibarra <mailto:wajalotnet@gmail.com>
>> 11 de octubre de 2017, 13:14
>> Hi Rudy
>>
>> 1- Yes, with all 4 disk plugged in, system does not boot
>> 2- Yes, with the broken disk unplugged, it boots
>> 3 - Yes, raid does not assemble during boot. I assemble manually doing
>>
>> root@grafico:/home/jose# mdadm --assemble --scan /dev/md0
>> root@grafico:/home/jose# mdadm --assemble --scan
>> root@grafico:/home/jose# mdadm --assemble /dev/md0
>>
>> 4 -When I try to mount
>>
>>   mount /dev/md0 /mnt
>>
>> mount: wrong file system, bad option, bad superblock in /dev/md0, 
>> missing codepage or helper program, or other error
>>
>>     In some cases useful info is found in syslog - try dmesg | tail or 
>> something like that.
>>
>> I do dmesg | tail
>>
>> root@grafico:/mnt# dmesg | tail
>> [  705.021959] md: pers->run() failed ...
>> [  849.719439] EXT4-fs (md0): unable to read superblock
>> [  849.719564] EXT4-fs (md0): unable to read superblock
>> [  849.719589] EXT4-fs (md0): unable to read superblock
>> [  849.719616] UDF-fs: error (device md0): udf_read_tagged: read 
>> failed, block=256, location=256
>> [  849.719625] UDF-fs: error (device md0): udf_read_tagged: read 
>> failed, block=512, location=512
>> [  849.719638] UDF-fs: error (device md0): udf_read_tagged: read 
>> failed, block=256, location=256
>> [  849.719642] UDF-fs: error (device md0): udf_read_tagged: read 
>> failed, block=512, location=512
>> [  849.719643] UDF-fs: warning (device md0): udf_fill_super: No 
>> partition found (1)
>> [  849.719667] isofs_fill_super: bread failed, dev=md0, iso_blknum=16, 
>> block=32
>>
>> Thanks a lot for your helping
>> Rudy Zijlstra <mailto:rudy@grumpydevil.homelinux.org>
>> 11 de octubre de 2017, 12:42
>> Hi Joseba,
>>
>>
>>
>> Let me see if i understand you correctly
>>
>> - with all 4 disks plugged in, your system does not boot
>> - with the broken disk unplugged, it boots (and from your description 
>> it is really broken, no DISK recovery possible unless by specialised 
>> company)
>> - raid does not get assembled during boot, you do a manual assembly?
>>      -> please provide the command you are using
>>
>> from the log above, you should be able to do a mount of /dev/md0 which 
>> would auto-start the raid.
>>
>> If that works, the next step would be to check the health of the other 
>> disks. smartctl would be your friend.
>> Another useful action would be to copy all important data to a backup 
>> before you add a new disk to replace the failed disk.
>>
>> Cheers
>>
>> Rudy
>
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