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



On 11/10/17 22:14, Joseba Ibarra wrote:

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

quoted

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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