NFS \"features\"

[Kemp at DOCKMASTER.NCSC.MIL]

Kenneth Almquist writes:
 > The advantage of the NFS approach is that /dev can be on a remote file
 > system rather that a local file system, thereby freeing up maybe 1K bytes
 > on the local machine. [ . . . ]  It strikes me as a bad tradeoff.

The reason /dev entries refer to devices on the local machine is NOT to
save a paltry 1K bytes of memory.  The reason is that the /dev directory
is just a symbol table that maps symbolic names into major and minor
device numbers, which in turn are used to index the bdevsw or cdevsw
arrays to get to the correct device driver subroutines.  The kernel is
(of course) running on your local machine, so you get your local device.

NFS is great, with its virtual-nodes referring to filesystem blocks on
remote machines, but do you really want to try to do that with arbitrary
devices?  A Network Tape System might be possible, if you don't mind
having to add a mount protocol to tell you which tape drive on your
network /dev/rst0 actually refers to.  I shudder to consider that scheme
in its full generality though - the Network Frame Buffer System, Network
A/D System, Network Array Processor System, etc.  etc.

  Dave Kemp <Kemp at dockmaster.ncsc.mil>