[Lustre-discuss] Quick writeback cache question

Andreas Dilger
Wed, 04 Mar 2009 09:41:21 -0000

On Mar 04, 2009  09:22 +0000, Daire Byrne wrote:
> ----- "Andreas Dilger" <adilger at sun.com> wrote:
> > Secondly, with small files there is also the overhead of creating
> > the many small files on the MDS, which will likely take as long
> > as the RPCs being sent to the OSTs with data.  There is not currently
> > a metadata writeback cache that allows files to be created only on
> > the client.  That is something we are examining, but it is still
> > a ways off.
>
> Ah yes of course. This is the performance bottleneck I''m seeing
over
> a high latency link. Thanks for the clarification.

You can increase the number of RPCs in flight for this client via
/proc/fs/lustre/osc/*/max_rpcs_in_flight, and it should improve small-file
IO performance.

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