[lustre-discuss] oldest lustre deployment?

[Latham, Robert J.]

On Thu, 2018-08-16 at 01:44 +0000, Andreas Dilger wrote:
> There is also the separate question of whether anyone running an
> ancient
> version of Lustre (which also requires an ancient kernel) will be
> updating
> their MPICH to the latest version?

Upgrading MPICH requires no privileges and no maintenance window.  I
would expect folks to upgrade MPICH frequently -- as I did/do on our
Blue Gene system for one example.

Upgrading Lustre has proven to be a somewhat more challenging process
for more than a few sites, based on the OpenSFS survey.

> In any case, it appears that the MPICH demands on llapi_layout_*()
> are
> fairly small, and it should be straight forward to implement stubs
> for the
> few functions that it is using (which are for non-PFL files).  If
> such
> an MPICH library is run against a newer version of Lustre, it will
> return
> some approximate values via the old interface, which may not be ideal
> but
> are no worse than runnnig an older MPICH library.

Indeed: one needs only implement 14 routines.

==rob