Re: NFS client behavior on WRITE_DELEGATION

Anna Schumaker
2018-12-05T20:30:06Z

(Resending due to accidentally using HTML instead of plain text)

On Wed, 2018-12-05 at 15:22 -0500, Anna Schumaker wrote:
> Hi Soumya,
>
> What conditions are you seeing the writes? It could be the kernel trying to
> flush out data to free up memory for other processes.
>
> I don't think preemptively writing back data is necessarily a bad thing
> though, even with a write delegation. If the server decides to recall the
> delegation, we wouldn't keep it waiting as long while we write back local
> data. Additionally, if the client crashes then any updates might have already
> had a chance to sync to the server.
>
> I hope this helps!
> Anna
>
> On Mon, Dec 3, 2018 at 2:55 AM Soumya Koduri <skoduri@redhat.com> wrote:
> > Hi,
> >
> > In our NFSv4.1 Delegations testing we observed that NFS client sends
> > WRITE requests to the server even when granted WRITE_DELEGATION. I see
> > that only OPEN/CLOSE and LOCK operations are served locally by the client.
> >
> > Please confirm if this behavior is expected and if yes, can it be
> > improved to avoid sending WRITEs to the server until the application
> > does fsync.
> >
> > Thanks,
> > Soumya