Re: Unable to re-assemble a raid 10 after it has FAILED.

[NeilBrown <neilb@suse.de>]

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On Tue, 10 Jun 2014 13:04:28 +0200 Alberto Morell <amp4tj@gmail.com> wrote:

> Hi!
> 
> I have a raid 10 devices with 4 components. I make the raid fails, by
> making two components fail (using "mdadm --set-faulty <device>"). When
> I add the two devices back, they are added as spare devices. Then, I
> can get the raid active again only creating the raid again using
> "mdadm --create --assume-clean...". Re-assembling the device does not
> work with error message:
> 
> mdadm: failed to RUN_ARRAY /dev/md/hdd: Input/output error
> mdadm: Not enough devices to start the array.
> 
> I am trying to automate the raid configuration and the "mdadm --create
> ..." option is not convenient as I would have to know all the creation
> parameters.
> 
> Below is the command sequence.
> 
> Thanks is advance,
> 
> Alberto Morell.
> 
> 
> [root@os2 raid_tools]# mdadm --version
> mdadm - v3.2.6 - 25th October 2012
> 
> [root@os2 ~]# mdadm --create /dev/md/hdd --metadata=1.0 --auto=md --name=hdd \
> --chunk=256 --bitmap=internal --bitmap-chunk=65536 --level=raid10 --run \
> --raid-devices=4 /dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1
> 
> [root@os2 ~]# mdadm --set-faulty /dev/md/hdd /dev/sde1
> mdadm: set /dev/sde1 faulty in /dev/md/hdd
> [root@os2 ~]# mdadm --set-faulty /dev/md/hdd /dev/sdf1
> mdadm: set /dev/sdf1 faulty in /dev/md/hdd

So now your array is dead.  I assume you expected this.

> 
> [root@os2 ~]# mdadm --remove /dev/md/hdd /dev/sde1
> mdadm: hot removed /dev/sde1 from /dev/md/hdd
> [root@os2 ~]# mdadm --remove /dev/md/hdd /dev/sdf1
> mdadm: hot removed /dev/sdf1 from /dev/md/hdd
> [root@os2 ~]# mdadm --add /dev/md/hdd /dev/sde1
> mdadm: re-added /dev/sde1
> [root@os2 ~]# mdadm --add /dev/md/hdd /dev/sdf1
> mdadm: re-added /dev/sdf1

Adding good things to dead things doesn't make the dead thing undead.
You don't want to do this.

If and array is dead, the best thing to do is to stop it, before trying to
re-add anything, and (after checking the all the devices are really working)
assemble with --force.
That is the best way to breath life into a dead array.

NeilBrown

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