Lustre discuss - Aug 2009 - multiple runs of lfsck with different options using same mds and ost db's

Can lfsck be run multiple times using different set of options (options like
-l -c and -d ) using the same set of mds and ost db''s.
For e.g what to expect if lfsck is run for coherence check after a MDS crash
in the following order

1.lfsck with -n (no fix)
2.lfsck to backup orphaned objects (-l option)
3.lfsck to delete  orphaned objects (will it find any after backup)
4.lfsck to  create missing OST objects MDS inodes (-c option).

In all the above runs same mdsdb and ostds''s were used.
Is it advisable/mandatory to recreate mdsdb and ostdb''s again after a
fix is
done using lfsck.
Can all the tasks mentioned above be accomplished in a single run (i.e. can
-l -d -c be specified together)?


-- 
Regards--
Rishi Pathak
National PARAM Supercomputing Facility
Center for Development of Advanced Computing(C-DAC)
Pune University Campus,Ganesh Khind Road
Pune-Maharastra
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On Aug 24, 2009  19:14 +0530, rishi pathak wrote:
> Can lfsck be run multiple times using different set of options (options
like
> -l -c and -d ) using the same set of mds and ost db''s.
> For e.g what to expect if lfsck is run for coherence check after a MDS
crash
> in the following order
> 
> 2.lfsck to backup orphaned objects (-l option)
> 3.lfsck to delete  orphaned objects (will it find any after backup)
Running both of these will cause problems.  The "-l" option will link
the objects into files in the lost+found directory, but then "-d" will
delete the objects, so now you have files in lost+found that are
referencing non-existent objects.
> 4.lfsck to  create missing OST objects MDS inodes (-c option).
> 
> In all the above runs same mdsdb and ostds''s were used.
> Is it advisable/mandatory to recreate mdsdb and ostdb''s again
after a fix is
> done using lfsck.
Yes.
> Can all the tasks mentioned above be accomplished in a single run (i.e. can
> -l -d -c be specified together)?
They can, though specifying both "-l" and "-d" will result
in "-d" taking
preference.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.