Re: Broken harddisk

["T. Ermlich" <pelegrine@gmx.net>]

Hi again,

well, due to that realy handy hints I subscribed to the list ... ;)

Gordon Henderson scribbled on 29.01.2005 16:56:
> On Sat, 29 Jan 2005, T. Ermlich wrote:
> 
>>That's right: each harddisk is partitioned absolutly identically, like:
>>     0 - 19456 - /dev/sda1 - extended partition
>>     1 - 6528  - /dev/sda5 - /dev/md0
>>  6529 - 9138  - /dev/sda6 - /dev/md1
>>  9139 - 16970 - /dev/sda7 - /dev/md2
>>16971 - 19456 - /dev/sda8 - /dev/md3
>>And after doing those partitionings I 'combined' them to act as raid1.
> 
>>I have two additional IDE drives in that system.
>>/dev/hda contains some data, and is the boot drive, /dev/hdb contains
>>some less important data.
> 
> Just as a point of note - if the boot disk goes down it will be harder to
> recover the data... Consider making the boot disk mirrored too!

Yeah .. I thought about that in the past ... and decided to buy an 3Ware 
controller (9500S-4LP) for those things in ~2-3 month (as I don't have 
the money yet).
Currently I'm using the onboard SATA controller (Asus A7V8X with an 
Promise controller),

>>>  mdadm --add /dev/md0 /dev/sda1
>>>  mdadm --add /dev/md1 /dev/sda2
>>>  mdadm --add /dev/md2 /dev/sda3
>>>  mdadm --add /dev/md3 /dev/sda4
>>
>>Now some new trouble starts ...?
>>'mdadm --add /dev/md0 /dev/sda1' started just fine - but exactly at 50%
>>it started giving tons of errors, like:
> 
> You should ve using:
> 
>   mdadm --add /dev/md0 /dev/sda5

Yes, I did - I just made a mistake when writing the command above.

>>[quote]
>>Jan 29 16:10:24 suse92 kernel: Additional sense: Unrecovered read error
>>- auto reallocate failed
>>Jan 29 16:10:24 suse92 kernel: end_request: I/O error, dev sdb, sector
>>52460420
> 
> The is a read error from /dev/sdb. What it's saying is that sdb has bad
> sectors which can't be recoverd.
> 
> You have 2 bad drives in a RAID-1 - and thats really bad )-:

All I have ... better than nothing ... will be improved in the future ;)

>>Personalities : [raid1]
>>md3 : active raid1 sdb8[1]
>>       19960640 blocks [2/1] [_U]
>>
>>md2 : active raid1 sdb7[1]
>>       62910400 blocks [2/1] [_U]
>>
>>md1 : active raid1 sdb6[1]
>>       20964672 blocks [2/1] [_U]
>>
>>md0 : active raid1 sdb5[1] sda5[2]
>>       52436032 blocks [2/1] [_U]
>>       [==========>..........]  recovery = 50.0% (26230016/52436032)
>>finish=121.7min speed=1050K/sec
>>unused devices: <none>
>>[/quote]
>>
>>Can I stop that process for /dev/md0, and start with /dev/md1 (just to
>>compare if its a problem with that partition only, or an general problem
>>(so that eg. the second drive has problens, too)? 
> 
> Yes - just fail & remove the drive partition:
> 
>   mdadm --fail   /dev/md0 /dev/sda5
>   mdadm --remove /dev/md0 /dev/sda5
> 
> At this point, I'd run a badblocks on the other partitions before doing
> the resync:
> 
>   badblocks -s -c 256 /dev/sdb6
>   badblocks -s -c 256 /dev/sdb7
>   badblocks -s -c 256 /dev/sdb8
> 
> if these pass, you can do the hot-add, however, it looks like the sdb disk
> is also faulty.
> 
> At this point, I'd be looking to replace both disks and restore from
> backup, but if you can re-sync the other 3 partitions, then remove the
> also-faulty sdb, and replace it with a new one, and you can re-sync the 3
> good partitions, and you only have to restore the '5' partition (md0) from
> backup.
> 
> You could try mkfs'ing the new partition sda5, mounting it, and copying
> the data on md0 over to it - theres a chance the bad sectors on sdb lie
> outside the filing system... This would save you having to restore from
> backup, however, it then becomes trickier as you then have to re-create
> the raid set on a new disk with a missing drive, and copy it again.

Ok, I'll do that.
I attached an older 80GB harddisk (/dev/hdc), and right now I'm copying 
the content of /dev/md0 there, using 'cp -a'.
If that's finished I'd start checking for badblocks ... and I guess the 
backups I made in the past might be full with probably damaged data ... :-(

Should I delete /dev/md0 completly after the copy-process has finished?
Or just checking for badblocks and continue using it?

>>btw: does mdadm also format the partitions?
> 
> No... You don't need to format/mkfs the partitions, as the raid resync
> will take care of making it a mirror of the existing working disk.

Ah .. ok. :-)

> Gordon

Thanks a lot!!
Torsten