[Lustre-discuss] free space of Lustre fs: unknown quantity?

[Thomas Roth]

Hi all,

on our test cluster I observe a rather large difference between "df" and 
"lfs df":

 >  lfs df  /lustre
 >  UUID                                 1K-blocks                Used 
                    Available    Use%   Mounted on
 >  ...
 >  filesystem summary:  137454163496     7056126648     130398036848 
  5%      /lustre

vs.
 > df  /lustre
 >  Filesystem                        1K-blocks                   Used 
            Available     Use%   Mounted on
 > mds at tcp0:/lust1         137454163496         73850360   130398036848 
   1%     /lustre

Using the human readable form, df -h, shows what this means: lfs 
believes that 6.6TB are in use, while the system thinks it's only 71GB. 
And of course, total and available space are equal.
I know that these tools for checking free and used disk space are 
notoriously imprecise. Not surprisingly then, "du -hs /lustre" gives me 
just 47 GB. I think I'd like to stick to "du" - gives best looking 
results ;-)

So, any ideas on what goes wrong here? Does something go wrong at all?

Oh, btw,  it is Lustre version 1.6.4.3 under Debian Etch 64 on this 
system. And I can observe this behavior on several clients, also after 
unmounting and remounting.

Regards,
Thomas