[Lustre-discuss] df and du difference on lustre fs

[Oleg Drokin]

Hello!

On May 26, 2011, at 8:19 AM, Ekaterina Popova wrote:

> We've installed lustre-client(2.0.0) and xen(4.0) on Debian squeeze. 
> Then we loaded img files with virtual machine images on lustre (images 
> were striped on 2 OSTs). VM started but then crashed. After that I tried 
> to remove img files from lustre. Client hangs and xen server hangs too. 

kernel messages from the hung instance would be interesting to see.

> After that I removed img files from another lustre client without any 
> problems and reboot xen server. When I make df -h it seems that img 
> files are on the lustre, but ls command doesn't show deleted files and 
> du -sm shows correct used space on lustre.

I assume that the "hung" client was holding the file open, then when you
unlinked the files from another client, only name got removed on MDS
and objects on OSTs remained.

> # df -h
> Filesystem            Size  Used Avail Use% Mounted on
> ...
> /dev/md13             2.7T   30G  2.6T   2% /ost2
> How can I fix it ?

Since you already killed the client holding the file open
once MDS registers the death of that client due to ping timeout,
it would close the descriptor and would proceed with destroying the
now orphan objects.

Alternatively next time your MDS restarts such orphaned objects should
also be destroyed.

Bye,
    Oleg
--
Oleg Drokin
Senior Software Engineer
Whamcloud, Inc.