Re: Raid 10 Issue

[Robin Hill <robin@robinhill.me.uk>]

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On Thu Mar 05, 2015 at 06:56:00PM +0100, Stefan Lamby wrote:

> Hello List.
> 
> I was setting up a new machine using ubuntu 14.04.02 lts using its installer,
> configuring a raid 10 with 2 disks and lvm on top of it. I was using 2 disks and
> now I like to add 2 more disks to the array so i want to end up with 4 disks, no
> spare.
> 
> Searching the internet I found that I am not able to --grow the array with the
> mdadm version this ubuntu is using (v3.2.5).
> Is that right?
> 
> So I decided to build a new array that way and try to move my data afterwards,
> which failed:
> (Is it OK to do it that way or do you recommend another?)
> 
> root@kvm15:~# mdadm --verbose --create --level=10 --raid-devices=4 /dev/md10
> missing missing /dev/sdc1 /dev/sdd1
> mdadm: layout defaults to n2
> mdadm: layout defaults to n2
> mdadm: chunk size defaults to 512K
> mdadm: /dev/sdc1 appears to be part of a raid array:
>     level=raid10 devices=4 ctime=Fri Feb 27 15:49:14 2015
> mdadm: /dev/sdd1 appears to be part of a raid array:
>     level=raid10 devices=4 ctime=Fri Feb 27 15:49:14 2015
> mdadm: size set to 1904165376K
> Continue creating array? y
> mdadm: Defaulting to version 1.2 metadata
> mdadm: RUN_ARRAY failed: Input/output error
>               <<<<<<<<<<<<<<<<<<<<<<<<<<<
> root@kvm15:~# 
>
IIRC, in a RAID10 setup, the redundant pair is held on adjacent drives.
You've specified two adjacent drives as missing, so the array cannot be
run. Try doing:
    mdadm --verbose --create --level=10 --raid-devices=4 /dev/md10 \
        missing /dev/sdc1 missing /dev/sdd1

HTH,
    Robin
-- 
     ___        
    ( ' }     |       Robin Hill        <robin@robinhill.me.uk> |
   / / )      | Little Jim says ....                            |
  // !!       |      "He fallen in de water !!"                 |

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