Vax 11/780 performance vs Sun 4/280 performance

[Dave Mason]

We are planning to replace 2 of our Vax 11/780s with  2 Sun 4/280s.
Each vax has 6 Mbytes of memory, 2 RA80 and 1 RA81, and 40 terminals.
The vaxes are currently running 4.3 BSD + NFS (from Mt Xinu).
Each sun is planned to have 32 Mbytes of memory, 2 of the new NEC
disk drives and will be running the same 40 terminals. The vaxes
are being used by undergrads doing pascal, f77 and C programming
(compile and bomb).  Most students use umacs (micro-emacs) as
their text editor.

What I was wondering is has anyone done a similiar type switchover?
Is there a horendous degradation of response when the load average gets
sufficiently high or does it degrade linearly with respect to load average?
Is overall performance of a Sun 4/280 better/worse/the same as a
similiarly loaded vax 11/780 (as configured above)?
Were there any surprises when you did the switchover?

My personal feeling is that we will win big, but the local DEC salesman
is making noises about Sun 4/280 performance, especially with > 15 users.
I just want to confirm if my opinion of the local DEC sales office is well
founded :-).

Please mail your responses. If there is sufficient interest I'll post
a summary to the net.

Thanks in advance for any comments.


				Dave Mason
				University of Calgary
				{ubc-cs,alberta,utai}!calgary!dave