[Lustre-discuss] Solved: incorrect num_osts; LBUG

Michael Sternberg sternberg at anl.gov
Sun Jan 4 12:25:08 PST 2009

I wrote:

On Jan 2, 2009, at 19:24 , Michael Sternberg wrote:
> While performing an LFSCK after upgrade lustre-1.6.6, the MDS claims
> to have 512 OSTs [while there is only 1]:
> 	MDS: num_osts = 512

Well, I found an interesting section "How to fix bad LAST_ID on an  
OST" in the operations manual, Appendix D, which pointed more or less  
in the right direction.

Briefly, /lov_objid within the MDS ldiskfs is constructed from /O/0/ 
LAST_ID in all the OSTs' ldiskfs.  In my case, with only one OST, the  
first and only entry agrees between these two files, and the rest of  
lov_objid was padded with NULs to 4KB (block size?).  I do not  
understand what caused this, but, given prior e2fsck output indicating  
length 8, I decided to simply chop off the NULs, which indeed made  
e2fsck happy.  lfsck on a client found a handful of empty orphans, but  
a backup on the client side still matches the contents of the rest of  
the fs (phew!).

Regards, Michael

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