recover linear mode raid howto

recover linear mode raid howto

[Костырев Александр Алексеевич]

Hello!
I'm trying to figure out how one can recover from linear mode crash.
I'm aware that from this type of mode I can recover only part of data, there's no redundancy in linear mode and that's ok for me.
I'm ok with part of it.

so far I'm trying to get it work in VM for now.


I've added two 50M disks to my VM.

and partiotioned them like this:
Device Boot      Start     End      Blocks  Id  System
/dev/vdb1        2048      102399   50176   fd  Linux raid autodetect
Device Boot      Start     End      Blocks  Id  System
/dev/vdc1        2048      102399   50176   fd  Linux raid autodetect

mdadm --create --verbose /dev/md0 --level linear --raid-disks 2 /dev/vdb1 /dev/vdc1
mdadm --detail --scan >> /etc/mdadm/mdadm.conf

mkfs.xfs /dev/md0 
mount /dev/md0 /mnt/linear/

mkdir /mnt/linear/etc
mkdir /mnt/linear/etc2
mkdir /mnt/linear/etc3

filled with some data
cp -r /etc/* /mnt/linear/etc/
cp -r /etc/* /mnt/linear/etc2/
cp -r /etc/* /mnt/linear/etc3/

df -h /dev/md0
Filesystem            Size  Used Avail Use% Mounted on
/dev/md0               92M   69M   23M  76% /mnt/linear

then I remove one disk from my VM

umount /mnt/linear
mdadm --stop /dev/md0

I've added another clear disk image 50M.

make partitions on new disk
sfdisk -d /dev/vdb | sfdisk /dev/vdc

how should I proceed ?

thanks a lot!

--
С уважением,
Костырев Александр
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ЗАО "Сервер-Центр"
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Re: recover linear mode raid howto

[keld]

On Tue, Jun 26, 2012 at 05:26:53PM +1100, ???????? ????????? ?????????? wrote:
> Hello!
> I'm trying to figure out how one can recover from linear mode crash.
> I'm aware that from this type of mode I can recover only part of data, there's no redundancy in linear mode and that's ok for me.
> I'm ok with part of it.
> 
> so far I'm trying to get it work in VM for now.
> 
> 
> I've added two 50M disks to my VM.
> 
> and partiotioned them like this:
> Device Boot      Start     End      Blocks  Id  System
> /dev/vdb1        2048      102399   50176   fd  Linux raid autodetect
> Device Boot      Start     End      Blocks  Id  System
> /dev/vdc1        2048      102399   50176   fd  Linux raid autodetect
> 
> mdadm --create --verbose /dev/md0 --level linear --raid-disks 2 /dev/vdb1 /dev/vdc1
> mdadm --detail --scan >> /etc/mdadm/mdadm.conf
> 
> mkfs.xfs /dev/md0 
> mount /dev/md0 /mnt/linear/
> 
> mkdir /mnt/linear/etc
> mkdir /mnt/linear/etc2
> mkdir /mnt/linear/etc3
> 
> filled with some data
> cp -r /etc/* /mnt/linear/etc/
> cp -r /etc/* /mnt/linear/etc2/
> cp -r /etc/* /mnt/linear/etc3/
> 
> df -h /dev/md0
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/md0               92M   69M   23M  76% /mnt/linear
> 
> then I remove one disk from my VM
> 
> umount /mnt/linear
> mdadm --stop /dev/md0
> 
> I've added another clear disk image 50M.
> 
> make partitions on new disk
> sfdisk -d /dev/vdb | sfdisk /dev/vdc
> 
> how should I proceed ?
> 
> thanks a lot!


Thaks for the effort. Maybe, when you have found a robust way to do it, then
you could add the description to our wiki, at https://raid.wiki.kernel.org/

(BTW, the wiki looks like it is open again for editing).

best regards
keld