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unused space before data offset mismatch

DISCUSSION kustep 3 participants 3 messages Nov 20, 2013 – Nov 21, 2013 MD RAID

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kustep

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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

#1 lore raw
Quoted 4 lines · kustep

Hello Everyone,

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

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

Quoted 5 lines

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

#2 lore raw
In reply to kustep
Quoted 4 lines · On Wed, 20 Nov 2013 20:46:21 +0100 kustep <[email protected]> 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

Quoted 20 lines

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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