[Lustre-discuss] Completely lost MGT/MDT

[Венедикт Федотов]

On 06/29/2013 12:24 AM, Dilger, Andreas wrote:
> On 2013/28/06 3:25 PM, "Andrus, Brian Contractor" <bdandrus at nps.edu> wrote:
> 
>> Basically, I was adding capacity to a system while doing a fresh install.
>> Turns out /dev/sda which used to be the disk in the bottom slot became
>> the disk in the top slot instead.
>> That happened to be where the MDT was, which was promptly repartitioned
>> and formatted.
>>
>> Not exactly something I was expecting....
> 
> Presumably you have no backups or snapshots of the MDT device?  Lustre can
> handle a lot of inconsistency between the MDT and OSTs, even without
> running lfsck.
> 
> Also, there was once a similar situation with a reformatted MDT that was
> partly recovered using the "ext3grep" utility.  This allowed finding the
> filename->inode mappings in the dirents in directory leaf blocks, and the
> ".." dirent allowed connecting the parent directories.  In Lustre 2.x, the
> "link" xattr on the MDT inodes could also be used to recover the filenames
> even if the directory entries are lost.

I guess you are referring to the recovery I did at DDN (*)? Actually,
ext3grep didn't do what we needed, so I wrote our own tool. In the mean
time Kit did another recovery, further improved the tools and uploaded
them to

http://code.google.com/p/decode-ost-attr/
http://code.google.com/p/mdt-recovery/

Cheers,
Венедикт


PS: Sorry, for some reasons I'm using an alias name.