From mboxrd@z Thu Jan  1 00:00:00 1970
From: Veljko <veljko3@gmail.com>
Subject: Re: Linear device of two arrays
Date: Mon, 17 Jul 2017 12:16:34 +0200
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On 07/15/2017 02:12 AM, NeilBrown wrote:

> So command should be
>
>>>   dd if=/dev/md2 of=SOMEWHERE/SAFE bs=1M skip=5626590
>
> and expect it to create a 3M file.
>
> Use this 'skip' number of the 'seek' number later.
>
> NeilBrown

Thanks, Neil, now it makes more sense.

I tried to create new linear device, but mdadm is complaining about 
data-offset:

# mdadm -C /dev/md4 -l linear -n 2 --rounding=1M -e 1.0 --data-offset=0 
/dev/md2 /dev/md3
  mdadm: invalid data-offset: 0

I'm using Debian 8.8 if it makes any difference.

# mdadm -V
  mdadm - v3.3.2 - 21st August 2014

What could be the problem?

Regards,
Veljko