[pnfs] MDS exporting pNFS and non-pNFS file systems

[Muntz, Daniel]

What are people doing to support exporting pNFS and non-pNFS file
systems from an MDS?  The information from EXCHANGE_ID is not
per-file-system, so can't be used to determine if a particular file
system is pNFS-enabled.  Based on talking with Ricardo and Mike, we were
thinking perhaps GETATTR could be used.  E.g., GETATTR could return a
layout type of 0 for entities that do not support pNFS.

Perhaps the IBMers have some thoughts on this.  If you had a server
exporting 2 GPFS file systems, and you wanted to export one with pNFS
and one without, how would you want to handle this in the protocol?  For
that matter, how would you want to handle it from a UI perspective?  For
GPFS, an /etc/exports flag might make sense.  This wouldn't really work
well for spNFS though.  For GPFS I assume you could switch back and
forth between exporting with/without pNFS.  For spNFS, you're committed
to exporting with pNFS (exporting without pNFS would result in access to
the files on the MDS).

  -Dan