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From: Neil Brown <neilb@suse.de>
To: roma1390 <roma1390@gmail.com>
Date: Wed, 13 May 2009 20:39:20 +1000
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Cc: linux-kernel@vger.kernel.org
Subject: Re: md: Can't convert raid level
In-Reply-To: message from roma1390 on Wednesday May 13
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On Wednesday May 13, roma1390@gmail.com wrote:
> Hello,
> 
> tested with linux-2.6.git a4f1cb9f3c42e5d278b0678ed5225d9331a8dcff
> 
> If i have spare disk i can grow
> raid1, raid4, raid5 and raid6
> 
> but can't convert to other raid level. Raid conversation matrix:
> 
> from\to | 0 | 1 | 4 | 5 | 6
> ============================
>   raid0  | -   -   -   -   -
>   raid1  | -   +   -   -   -
>   raid4  |-22 -22  +  -22 -22
>   raid5  |-22 -22 -22  +  -22
>   raid6  |-22 -22 -22 -22  +
> 
> Sample test script, log, dmesg, kernel config is attached.
> 
> Major problem is than can not do online covert from raid5 to raid6:

Correct.  This functionality has not been implemented yet.

The kernel contains the required support, but mdadm does not make use
of it correctly yet.

NeilBrown