[Lustre-discuss] recovering formatted OST

Wojciech Turek wjt27 at cam.ac.uk
Wed Oct 20 08:06:58 PDT 2010


Thank you for quick reply.
Unfortunately all partitions were formatted with ext3, also I didn't mention
earlier but the OST was placed on the LVM volume which is now gone as the
installation script formatted the physical device. I understand  that this
complicates things even further. In that case i guess firstly I need to try
to recover the LVM information otherwise fsck will not be able to find
anything is that right?

Best regards,

Wojciech

On 20 October 2010 08:46, Andreas Dilger <andreas.dilger at oracle.com> wrote:

> On 2010-10-19, at 17:01, Wojciech Turek wrote:
> > Due to the locac disk failure in an OSS one of our /scratch OSTs was
> formatted by automatic installation script. This script created 5 small
> partitions and 6th partition consisting of the remaining space on that OST.
> Nothing else was written to that device since then. Is there a way to
> recover any data from that OST?
>
> Your best bet is to make a full "dd" backup of the OST to a new device (for
> safety), first restore the original partition table.  If there was not
> originally a partition table, then you can just erase the new partitions:
>
>  dd if=/dev/zero of=/dev/XXX bs=512 count=1
>
> Then run e2fsck -fy, followed by "ll_recover_lost_found_objs" (from a newer
> lustre RPM, if you don't have it).  It is likely that you will get some or
> most of the data back.  This depends heavily on exactly what was written
> over the original filesystem.
>
> If it was just a new partition table, there should be relatively little
> damage (ext3 is very robust this way, and can repair itself so long as the
> starting alignment is correct).  If there were filesystems formatted in each
> of these partitions, then the amount of data available will be reduced
> significantly.
>
> Cheers, Andreas
> --
> Andreas Dilger
> Lustre Technical Lead
> Oracle Corporation Canada Inc.
>
>
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