Unix on the Vax 8600

[peterb at pbear.UUCP]

	Since the 8600 still uses the same I/O structure as the 780's, heavy
swap will slow a 8600 down. Think of it this way, where will 2 780's
connected by ethernet be slower than an 8600? The answer is in inter machine
conversation, so the converse shoul ~ be true also.

	Piling on more users to an 8600 will slow I/O somewhat since the
unibus is still there, but cpu intensive processes will excell on the 8600.
disk to disk transfer's such as copying, etc will be just about as fast. The
kernel will run faster allocating resources and resolving scheduling, but
many problems will be limited to the speed of I/O, and this controls overall
throughput for edit sessions.

	If your users are running through the edit/compile phase most of the
time, a possible step prior to aquiring ab 8600 is to try for the best of
all worlds, namely pile your user's terminals on one 780 and do the compiles
on the other. This way the I/O 780 is doing mostly slow I/O terminal work
without cpu intensive operations slowing down the I/O (such as compiles).
On the other 780, the cpu intensive work will not have the massive I/O
overhead of supporting terminals and their inherent speed. It will sit in
cpu intensive state most (if not all) of the time.

	This situation presumes that you ethernet to two together and remove
the distinction from the user by placing shell scripts in fromt of the
compilers. It may not work perfectly, but average throughput should increase
as you can tune each machine for a different environment, therby maximizing
the throughput.

	Hope it helps. If all else fails, find an 8600 and run your own
backyard benchmarks.

	Peter Barada
	{ihnp4!inmet|{harvard|cca}!ima}!pbear!peterb