On Tue, Jun 10, 2014 at 1:30 PM, NeilBrown [off-list ref] wrote:

On Tue, 10 Jun 2014 13:04:28 +0200 Alberto Morell [off-list ref] wrote:

quoted

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.

quoted

[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

That sequence solved the problem:
1. After the array is dead, stop it

[root@os2 raid_tools]# mdadm --stop /dev/md127
mdadm: stopped /dev/md127

2. Then, assemble the array with the proper components.

[root@os2 raid_tools]# mdadm --assemble /dev/md/hdd --force --run
--uuid=085d48f6:e6e38d1c:a476006f:cd3a3e51 --verbose /dev/sdc1
/dev/sdd1 /dev/sde1 /dev/sdf1

The array started with only three components, but then I added the
fourth just with a "mdadm --add"

(Before, I was first re-adding the failed components, and after that,
stopping and re-assembling the array)

Thanks a lot!

Alberto Morell.