NFS fun

[Mark Wallen]

When one runs NFS, there are some additional
interesting things that seem to become possible.

For instance, you could really run dual ported disks
between two systems.  The old bugaboo with dual porting
your drives was that only one port could be read/write,
so that you didn't completely scramble your disk.
And moreover, when lots of in core caching of disk data
was done (like UNIX likes to), the readonly port still gets
only an inconsistent view of the disk.  In the brave new world
of NFS, you would have your read/write port as usual, but the
second system mounts the disk as a NFS partition from the
read/write host.  So far you have bought nothing; but when
the NFS server crashes then you umount the NFS partition
and mount the file system (perhaps an fsck would be prudent :-)
on the second system.  With clever software, the original
NFS server would become the client when it came back up!

Also, it seems as though it would be possible to build a
"left handed" NFS server.  That is, one that read up
a remote/foreign file system (byte swap, etc) from a local
disk.  Thus, one should be able to use different hosts
(e.g., sun and vax) to implement the dual port scheme above.
(Of course, you probably also want a left hand fsck and dump).

Has anyone else thought of this (and found the holes)?  Anyone
actually done it?

Mark Wallen

Institute for Cognitive Science
UC San Diego

ucbvax!sdcsvax!sdics!wallen.uucp
wallen at ucsd.edu
wallen at nprdc.arpa