🚀 go-pugleaf

NFS reading plus NNTP posting has found favor in many large installations.

My (informal) observation seems to show NFS presents a lighter load
on the server than NNTP (provided the folks in your plant to run
daily "find" commands to purge core files and the like).
Context switch overhead from NFS daemons is limited by the number you
choose to run, while there are typically no limits to the number of
running NNTP daemons.  Further, some UNIX implementations recognize 
"interchangeable" service daemons and can avoid switching nfsd's,
which substantially improves system throughput.

On the other hand, posting via NFS is fraught with problems (security
and concurrent postings top the list).  In contrast, NNTP posting with
a "mini-inews" is simple.  One drawback to NNTP posting is that there
can be a delay between posting and getting feedback; it's possible a
post will fail without the user getting negative acknowledgment.
Creaky old pyramid still runs B news, and I regularly see failed
postings in /usr/spool/news/.bad; C news typically batches its input,
so I believe you can have similar problems there.  (If you were to run
INN on your server, posting delays would not be a problem, though
you've said you will use C news).

Addressing the original questions:

| Firstly: would a purely NFS solution work?

You can do it, but you probably won't be happy in the long
run because of posting problems.

| Secondly: (taking into account the bandwidth bottleneck at
| our router (which will have to handle newsflow in both
| directions, since we will _not_ be moving the router which
| is our Internet connection to net Y)) are there obvious
| benefits to one or the other approach?

If you want to throttle things way down, setting a low load
threshold in your NNTP server would probably be most effective.
Otherwise, if you want to maximize throughput, I would use
NFS for reading.

| Thirdly: is there a hybrid or other approach that would be
| superior to either of these?

My preference is outlined above.

| Finally: if the NFS solution is deemed preferable, would
| using NNTP or rsh for posting be better?

NNTP is probably better in the long run.  If your installation
grows, rsh access problems will grow even faster; if you use
NNTP, I suspect maintenance will be easier.
--
"Here, take my advice, er, umbrella.  I'm not using it myself..."