From: rkoehler@author.gsfc.nasa.gov (Bob Koehler)
Subject: Re: What makes Unix Special?
News-Software: VAX/VMS VNEWS 1.4-b1  
Organization: CSC System Sciences Division
Date: Mon, 11 Jan 1993 14:34:00 GMT

In article <1993Jan9.125052.12247@bronte.boeing.com>, paula@atc.boeing.com writes...
> 
>Bryan was talking about the NFS automounter known as "amd".  Since you seem to
>have a strong negative opinion of NFS, would you care to compare it with other
>file-sharing protocols.  I'd love to hear NFS contrasted with Andrew, but
>RFS and DECnet are also somewhat interesting.
> 

 Thanks for the info.  NFS happens to be hosing my ethernet (I've measured it),
so I've some to agree with all the folks who told me it would.  I don't know
anything about RFS (what is it, please?).  DECnet (available from a lot of
vendors on a lot of systems, despite being "DEC"net) capabilities vary from
implementation to implementation, even from DEC.  Startup of a DECnet
connection can be slow if steps are not taken to speed it up.  "file sharing"
under DECnet simply comes from it's ability to suport file opens/creates across
a network, allowing record by record (or byte by byte) manipulation of a file
on a remote system.  Systems that employ locking techniques within the file
system will typically enforce those locks on the system where the file resides.
(Boy, is that a brief rundown).

DFS is an NFS-like file sharing implemented on top of DECnet.  It has better
performance in many aspects, but I've only seen it implemented on VMS, and I
don't know anyone whose actually using it.

We rely on VMScluster between our VMS machines, which not only gives us
location transparency, it also give us distributed locking (all nodes see
all locks of interest), and does not hose the ethernet (I've measued it, too). 
Of course, you absolutely must have VMS to use it.

We use LAST between our DOS and VMS machines, also available for UNIX, OS/2,
and Mac.  It works and doesn't seem to be hosing our ethernet, but it doesn't
currently give you UNIX-to-UNIX like NFS.

>Mr. Koehler seems to imply that NFS is a particularly ineffecient protocol.
>OK.  That may be true.  Is there another file-sharing protocol that's as
>widely available as NFS and uses network bandwidth more effectively?  I
>have a busy net, and will be happy to listen to suggestions for ways to
>improve service to my users.

If I knew of any widely avialable alternatives do you think I'd still be
using NFS?  I have to have something that will tie together HP-UX, Ultrix, AIX,
optionaly VMS, and soon DOS, as well as possibly Mac.

NFS was of course, built on top of TCP/IP.  TCP/IP being meant to survive
possibly noisy wide area communications simply may not be as good a choice for
a reasonably clean LAN as some of the other protocols.  If NFS had been built
on top of something else (like adding a layer or 2 to sit right on top of
Ethernet) it might be more efficient, but then you would loose wide-area NFS,
or have to have NFS implemented over at least 2 protocols.

Of course, I'm watching the ISO/OSI space for capabilities in this area, but
I'm not holding my breath.  Someday soon I hope to have at least FTAM running
between two disimmilar OSs.

------------------------------------------------------------------------------
Bob Koehler                     |   Any illusion to these opinions being other
rkoehler@author.gsfc.nasa.gov   |   than just mine alone is just that.