Re: Corrupted ext4 filesystem after mdadm manipulation error

["L.M.J" <linuxmasterjedi@free.fr>]

Le Thu, 24 Apr 2014 16:22:49 -0400,
"Scott D'Vileskis" <sdvileskis@gmail.com> a écrit :

> I have been replying directly to you, not to the mailing list, since your
> case seems to be a case of user-screwed-up-his-own-data, and not a problem
> with mdadm/linux raid, nor a problem that will necessarily help someone
> else (since it is not likely someone will create a mess in exactly the same
> manner you have) .

Ha OK. 



> To summarize:
> 1) You lost a disk. Even down a disk, you should have been able to
> run/start the array (in degraded mode) with only 2 disks, mounted the
> filesystem, etc.
Yes of course, it worked only with 2 disks the last 3 weeks.


> 2) You then should have simply partitioned and then --add 'ed the new disk.
>   mdadm would have written a superblock to the new disk, and resynced the
> data
> 
> I assume your original disks were in the order sdb, sdc, sdd.

Exactly


> Unfortunately, you might have clobbered your drives by recreating the
> array. You certainly clobbered your superblocks and changed the order when
> you did this:
> > ~# mdadm -Cv /dev/md0 --assume-clean --level=5 --raid-devices=3 /dev/sdc1
> /dev/sdd1 /dev/sdb1
> 
> You changed the order, but because of the assume-clean, it shouldn't have
> started a resync of the data. Your file system probably had a fit though.
> 
> Hindsight is 20/20, a mistake was made, it happens to all of us at some
> point or another, (I've lost arrays and filesystems with careless use of
> 'dd' once upon a time, once I was giving a raid demo to a friend with loop
> devices, mistyped something, and blew something away)
> 
> IMPORTANT: At any point did your drives do a resync?

Unfortunatly : yes, resync occurs when I 



> Assuming no, and assuming you haven't done any other writing to your
> disks(besides rewriting the superblocks), you can probably correct the
> order of your drives by reissuing the --create command with the two
> original drives, in the proper order, and the missing drive as the
> placeholder. (This will rewrite the superblocks again, but hopefully in the
> right order)
> mdadm -Cv /dev/md0 --level=5 --raid-devices=3 missing /dev/sdc1 /dev/sdd1
> 
> If you can start that array (it will be degraded with only 2/3 drives) you
> should be able to mount and recover your data. You may need to run a full
> fsck again since your last fsck probably made a mess.

I shutdown the computer, remove the old disk, added the new one. Maybe I've messed up with SATA cables too.
Unfortunately, I use to start the degraded array like this :

~# mdadm --assemble --force /dev/sdc1 /dev/sdd1

didn't work

I created a partition on sdb, and then, the mistake
~# mdadm --stop /dev/md0
~# mdadm -Cv /dev/md0 --assume-clean --level=5 --raid-devices=3 /dev/sdb1 /dev/sdc1 /dev/sdd1

Didn't work better, then
~# mdadm --stop /dev/md0
~# mdadm --create /dev/md0 --level=5 --assume-clean --raid-devices=3 /dev/sdc1 /dev/sdd1 missing
~# mdadm --manage /dev/md0 --add /dev/sdb1 


Looks even worst, isn't it ?



> 
> Assuming you can mount and copy your data, you can then --add your 'new'
> drive to the array with the --add argument. (Note, you'll have to clear
> it's superblock or mdadm will object)
> 


And what do you think of files fsck may recovered :

5,5M 2013-04-24 17:53 #4456582
5,7M 2013-04-24 17:53 #4456589
 16M 2013-04-24 17:53 #4456590
 25M 2013-04-24 17:53 #4456594
 17M 2013-04-24 17:53 #4456578
 18M 2013-04-24 17:53 #4456580
1,3M 2013-04-24 17:54 #4456597
1,1M 2013-04-24 17:54 #4456596
 17M 2013-04-24 17:54 #4456595
2,1M 2013-04-24 17:54 #4456599
932K 2013-04-24 17:54 #4456598



Well, what should I do now ? mkfs everything and restart from scratch ?
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