[BlueOnyx:11230] Re: MD RAID device state="clean, degraded" -- how to fix

[Michael Stauber]

Hi Bob,

> I have a Dell server that I installed 5108.  It has two (2) 1GB drives 
> and one (1) 2GB disk.  When I installed it, I used the option to mirror 
> (soft RAID) across the drives but when I did it used all three drives.  
> I used "mdadm" to fail and remove the third (2GB) drive.  (I did not 
> want it part of the root mirror)  Now the device shows "clean, degraded" 
> when I list it with mdadm:
> 
> # mdadm --detail /dev/md0
> /dev/md0:
>          Version : 1.0
>    Creation Time : Fri Jul 20 07:38:36 2012
>       Raid Level : raid1
>       Array Size : 511988 (500.07 MiB 524.28 MB)
>    Used Dev Size : 511988 (500.07 MiB 524.28 MB)
>     Raid Devices : 3
>    Total Devices : 2
>      Persistence : Superblock is persistent
> 
>      Update Time : Tue Aug 28 16:25:57 2012
>            State : clean, degraded
>   Active Devices : 2
> Working Devices : 2
>   Failed Devices : 0
>    Spare Devices : 0
> 
>             Name : localhost.localdomain:0
>             UUID : 8b68d22d:4566147a:621a50a4:6d016578
>           Events : 325
> 
>      Number   Major   Minor   RaidDevice State
>         0       8        1        0      active sync /dev/sda1
>         3       8       17        1      active sync /dev/sdb1
>         2       0        0        2      removed
> #

I don't know the device of the third disk. But I assume it is /dev/sdc?

If so, did you really do both steps (fail and remove)? I know, you said
you did, but I'm just making sure. :-)

mdadm --fail /dev/md0 /dev/sdc1
mdadm --remove /dev/md0 /dev/sdc1

It may also be helpful to zero the superblock of the removed disk, as it
still contains RAID meta data which mdadm might see:

mdadm --zero-superblock /dev/sdc

If you did all those steps, it still could be that the disk is listed in
mdadm.conf, so you'd need to update the conf this way:

mdadm --detail --scan >> /etc/mdadm.conf

This appends to /etc/mdadm.conf, so you will have to edit the file
afterwards to remove duplicate lines. Your new ARRAY lines will be at
the end of this file.

For more information you might want to check this URL:

http://www.ducea.com/2009/03/08/mdadm-cheat-sheet/

-- 
With best regards

Michael Stauber