[CentOS] Re: Cannot re-make a software raid pair

Will McDonald wmcdonald at gmail.com
Thu Oct 5 23:00:38 UTC 2006

On 05/10/06, Nigel Kendrick <support-lists at petdoctors.co.uk> wrote:
> [root at petdoctors ~]# mdadm /dev/md1 -a /dev/hdg3
> mdadm: hot add failed for /dev/hdg3: Invalid argument
> [root at petdoctors ~]#

I don't know md at all well, but from a quick RTFM, has the previous,
faulty /dev/hdg3 been removed from the software RAID device?


Users of mdadm can run the command

# mdadm --detail /dev/md1

Now you've seen how it goes when a device fails. Let's fix things up.
First, we will remove the failed disk from the array. Users of mdadm
can run the command

# mdadm /dev/md1 -r /dev/sdc2

Now we have a /dev/md1 which has just lost a device. This could be a
degraded RAID or perhaps a system in the middle of a reconstruction
process. We wait until recovery ends before setting things back to

So the trip ends when we send /dev/sdc2 back home. As usual, you can
use mdadm instead of raidtools. This should be the command

# mdadm /dev/md1 -a /dev/sdc2

As the prodigal son returns to the array, we'll see it becoming an
active member of /dev/md1 if necessary. If not, it will be marked as
an spare disk. That's management made easy.


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