unused space before data offset mismatch

unused space before data offset mismatch

[kustep]

Hello Everyone,

is there an option to specifiy the "Unused Space : before=...."
Superblock information in mdadm -C ....?

My Raid crashed due to a controller error, but I was able to make the
new superblock almost identical to the old one (using mdadm -C
--assume-clean --level=6 --raid-devices=11 --chunk=256K --metadata=1.2
--bitmap=None --size=195328588 --data-offset=128768 /dev/md0
/dev/mapper/disk[cdefmbjkh] missing). Looking at mdadm --examine the
only difference left is:
old layout: Unused Space : before=257456 sectors, after=197632 sectors
new layout: Unused Space : before=257448 sectors, after=197632 sectors

Is there an option to change that or anything else I can do to make the
layouts identical? The assembled raid refuses to mount, and I suspect
this difference to be the reason.

Thanks in advance
Stephan

Re: unused space before data offset mismatch

[Phil Turmel]

On 11/20/2013 02:46 PM, kustep wrote:
> Hello Everyone,
> 
> is there an option to specifiy the "Unused Space : before=...."
> Superblock information in mdadm -C ....?

I don't know about this, but ...

> My Raid crashed due to a controller error, but I was able to make the
> new superblock almost identical to the old one (using mdadm -C
> --assume-clean --level=6 --raid-devices=11 --chunk=256K --metadata=1.2
> --bitmap=None --size=195328588 --data-offset=128768 /dev/md0
> /dev/mapper/disk[cdefmbjkh] missing). Looking at mdadm --examine the

This almost certainly didn't do what you think--square brackets in the
shell don't maintain the order of the letters given.  The device order
actually given to mdadm would have been [bcdefhjkm].  The bracket
notation will also leave out devices that don't actually exist.  You
need to use curly braces with commas to maintain a specific order.

FWIW,

Phil

Re: unused space before data offset mismatch

[NeilBrown]

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On Wed, 20 Nov 2013 20:46:21 +0100 kustep <kustep@web.de> wrote:

> Hello Everyone,
> 
> is there an option to specifiy the "Unused Space : before=...."
> Superblock information in mdadm -C ....?

 --data-offset=....

or 
  --data-offset=variable ... /dev/foo:16K  /dev/foo2:32K ....

You probably need mdadm 3.3.

NeilBrown

> 
> My Raid crashed due to a controller error, but I was able to make the
> new superblock almost identical to the old one (using mdadm -C
> --assume-clean --level=6 --raid-devices=11 --chunk=256K --metadata=1.2
> --bitmap=None --size=195328588 --data-offset=128768 /dev/md0
> /dev/mapper/disk[cdefmbjkh] missing). Looking at mdadm --examine the
> only difference left is:
> old layout: Unused Space : before=257456 sectors, after=197632 sectors
> new layout: Unused Space : before=257448 sectors, after=197632 sectors
> 
> Is there an option to change that or anything else I can do to make the
> layouts identical? The assembled raid refuses to mount, and I suspect
> this difference to be the reason.
> 
> Thanks in advance
> Stephan
> --
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