Re: Linear device of two arrays

[NeilBrown <neilb@suse.com>]

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On Mon, Jul 17 2017, Veljko wrote:

> 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

Bother.
 mdadm uses "parse_size()" to parse the offset, and this rejects
 "0", which makes sense for a size, but not for an offset.

 Just leave the "--data-offset=0" out. I checked and that is defintely
 the default for 1.0.

> I noticed that md2 and md3 use 1.2 metadata. Can that be the issue? 

No the metadata on md4 is quite independent of the metadata on md2 and md3.

NeilBrown


>
> 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
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