On Sat, 04 May 2013 13:13:27 +0200 Stefan Borggraefe [off-list ref]
wrote:

Am Freitag, 3. Mai 2013, 10:38:52 schrieben Sie:

quoted

On Thu, May 2, 2013 at 2:24 PM, Stefan Borggraefe [off-list ref] 

wrote:

quoted

quoted

I am using a RAID5 software RAID on Ubuntu 12.04

It consits of 6 Hitachi drives with 4 TB and contains an ext 4 file
system.

When I returned to this server this morning, the array was in the
following
state:

md126 : active raid5 sdc1[7](S) sdh1[4] sdd1[3](F) sde1[0] sdg1[6] sdf1[2]

      19535086080 blocks super 1.2 level 5, 512k chunk, algorithm 2 [6/4]

[U_U_UU]

sdc is the newly added hard disk, but now also sdd failed. :( It would be
great if there was a way to have the this RAID5 working again. Perhaps
sdc1
can then be fully added to the array and after this drive sdd also
exchanged.

I have had a few raid6 fail in a similar fashion: the 3rd drive
faliing during rebuild (Also 4 TB Hitachi by the way).

I tested if the drives were fine:

  parallel dd if={} of=/dev/null bs=1000k ::: /dev/sd?

And they were all fine. 

Same for me.

quoted

With only a few failing sectors (if any) I figured that very little
would be lost by forcing the failing drive online. Remove the spare
drive, and force the remaining online:

  mdadm -A --scan --force

I removed the spare /dev/sdc1 from /dev/md126

with

mdadm /dev/md126 --remove /dev/sdc1

After mdadm -A --scan --force the array is now in this state

md126 : active raid5 sdh1[4] sdd1[3](F) sde1[0] sdg1[6] sdf1[2]
      19535086080 blocks super 1.2 level 5, 512k chunk, algorithm 2 [6/4] 
[U_U_UU]

Did you stop the array first?
  i.e.
    mdadm --stop /dev/md126
    mdadm -Asfvv

NeilBrown

quoted

Next step is to do fsck.

I think this is not possible yet at this point. Don't I need to reassemble the 
array using the --assume-clean option and with one missing drive first? Some 
step is missing here.

Stefan
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