mdadm Raid level change from 1 to 5?

mdadm Raid level change from 1 to 5?

[Hans Kraus]

Hi,

I have a Raid 1 with 3 drives, the following layout (the internal
bitmap is already removed):
-----------------------------------------------------------------
md20 : active raid1 sdj1[2] sdi1[1] sdn1[0]
       732442432 blocks super 1.2 [3/3] [UUU]
-----------------------------------------------------------------
I tried to change it to Raid 5, but I'm getting aways an error.
-----------------------------------------------------------------
mdadm --grow /dev/md20 --level=5 --raid-devices=3 -c 32 \
   --backup-file=/home/kraush/work/raidLevelChange

Impossibly level change request for RAID1
-----------------------------------------------------------------
I tried it with various permutations (+/- raid-devices, c, ...).

Is something in my command wrong or is the level change not
possible?
This is on Debian 7, mdadm - v3.3-65-g2167de7 - 11th March 2014

Regards, Hans

Re: mdadm Raid level change from 1 to 5?

[Robin Hill]

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On Fri May 08, 2015 at 11:18:44AM +0200, Hans Kraus wrote:

> Hi,
> 
> I have a Raid 1 with 3 drives, the following layout (the internal
> bitmap is already removed):
> -----------------------------------------------------------------
> md20 : active raid1 sdj1[2] sdi1[1] sdn1[0]
>        732442432 blocks super 1.2 [3/3] [UUU]
> -----------------------------------------------------------------
> I tried to change it to Raid 5, but I'm getting aways an error.
> -----------------------------------------------------------------
> mdadm --grow /dev/md20 --level=5 --raid-devices=3 -c 32 \
>    --backup-file=/home/kraush/work/raidLevelChange
> 
> Impossibly level change request for RAID1
> -----------------------------------------------------------------
> I tried it with various permutations (+/- raid-devices, c, ...).
> 
> Is something in my command wrong or is the level change not
> possible?
> This is on Debian 7, mdadm - v3.3-65-g2167de7 - 11th March 2014
> 
I think you'll need one of the disks to be spare first. Try reducing the
RAID1 to a 2-disk plus spare configuration, then rerunning the grow.
Alternately you'd need to add a new disk as a spare first, then grow to
a 4 disk RAID5.

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

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Re: mdadm Raid level change from 1 to 5?

[Hans Kraus]

Thanks a lot, that was it. After fail & remove one HD, set
--raid-devices=2 and re-add the removed HD as spare, the --grow worked.

Regards, Hans

Am 08.05.2015 um 12:47 schrieb Robin Hill:
> On Fri May 08, 2015 at 11:18:44AM +0200, Hans Kraus wrote:
>
>> Hi,
>>
>> I have a Raid 1 with 3 drives, the following layout (the internal
>> bitmap is already removed):
>> -----------------------------------------------------------------
>> md20 : active raid1 sdj1[2] sdi1[1] sdn1[0]
>>         732442432 blocks super 1.2 [3/3] [UUU]
>> -----------------------------------------------------------------
>> I tried to change it to Raid 5, but I'm getting aways an error.
>> -----------------------------------------------------------------
>> mdadm --grow /dev/md20 --level=5 --raid-devices=3 -c 32 \
>>     --backup-file=/home/kraush/work/raidLevelChange
>>
>> Impossibly level change request for RAID1
>> -----------------------------------------------------------------
>> I tried it with various permutations (+/- raid-devices, c, ...).
>>
>> Is something in my command wrong or is the level change not
>> possible?
>> This is on Debian 7, mdadm - v3.3-65-g2167de7 - 11th March 2014
>>
> I think you'll need one of the disks to be spare first. Try reducing the
> RAID1 to a 2-disk plus spare configuration, then rerunning the grow.
> Alternately you'd need to add a new disk as a spare first, then grow to
> a 4 disk RAID5.
>
> HTH,
>      Robin
>

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