[Lustre-discuss] Swap on Lustre (was: Client is not accesible when OSS/OST server is down)

Andreas Dilger adilger at sun.com
Fri May 9 12:08:20 PDT 2008


On May 09, 2008  12:57 -0400, Robin Humble wrote:
> On Fri, May 02, 2008 at 11:25:03AM -0700, Andreas Dilger wrote:
> >Note that in 1.6.4+ there is an interface to export a block device
> >more directly from Lustre instead of using the loopback driver on top
> >of the client filesystem.  This is the "llite_loop" module and is
> >configured like:
> >
> >	lctl blockdev_attach {loopback_filename} {blockdev_filename}
> >
> >where {loopback_filename} is the file that should be turned into a
> >block device (it can be sparse if desired) and {blockdev_filename}
> >is the full filename that the new block device should be created at.
> 
> cool! I was wondering that that module was for.
> I'm trying to use it like:
>   lctl blockdev_attach /dev/lloop0 /some/file/on/lustre
> but then dd to /dev/lloop0 seems to go at ~kB/s wheras dd to the file
> goes at >= 100MB/s. am I doing something wrong?

Hmm, the code is virtually identical to the loop driver, so this is
a bit strange.  Could you grab the IO stats at the OST in
/proc/fs/lustre/obdfilter/{ostname}/brw_stats (use "lfs getstripe"
to determine which OST the file lives on) to see what kind of RPCs
are being sent to the server.

It might be that the lloop driver isn't setting up an elevator properly,
or is just sending the RPCs 4kB at a time...

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




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