Many thanks for prompt reply, On 20 October 2010 16:32, Andreas Dilger <[email protected]> wrote:
> Right - you need to recreate the LV exactly as it was before. If you > created it all at once on the whole LUN then it is likely to be allocated in > a linear way. If there are multiple LVs on the same LUN and they were > expanded after use the chance of recovering them is very low. > There was one LVM on that LUN I created it using following commands: pvcreate /dev/sdc vgcreate ost16vg /dev/sdc lvcreate --name ost16v -l 100%VG ost16vg So in order to recreate that LVM on the formatted LUN i need to repeat above steps, is that right? > In the e2fsprogs there is a tool I wrote called findsuper to scan a device > looking for ext3 superblock signatures. If needed, you could run findsuper > to determine the starting offset of the filesystem, and then just create a > simple partition with the right starting offset on order to run e2fsck. > Should I successfully recreate the LVM volume I will run findsuper tool on that volume. If the tool finds a superblock how I can tell if that superblock belongs to the ldiskfs and not to the newly created filesystems? > > That said, if there were filesystems formatted in each partition, the > amount of data loss may be large. You may have some saving grace if the > first partitions are very small and fit inside the space previously used by > the 400MB journal. > Unfortunately new partitions use much more space than 400mb 8 32 7809904640 sdc 8 33 10484719 sdc1 8 34 4193280 sdc2 8 35 4193280 sdc3 8 36 8387584 sdc4 8 37 7782640640 sdc5 > Cheers, Andreas > > On 2010-10-20, at 9:06, Wojciech Turek <[email protected]> wrote: > > 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 < <[email protected]> > [email protected]> 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. >> >> > -- Wojciech Turek Senior System Architect High Performance Computing Service University of Cambridge Email: [email protected] Tel: (+)44 1223 763517
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