UNIX as a back-end machine?

[John Menges]

Here at UNC, we have one VAX 11/780 with 4 Mbytes of
memory running 4.2bsd as the 'home machine' for
about 300 users.  (We also have 4 other VAXes running
4.2bsd for more specialized applications).  The 'main'
VAX is used primarily for text editing (vi, emacs),
communication (mail, news, uucp), classes (yacc, lex, cc),
VLSI design (mextra, lyra), and text processing (tex, troff).

We will soon be installing another VAX 11/780 with
8 Mbytes of memory, which will soon be upgraded to a
785.  Our existing VAX will probably be similarly
upgraded (8 Mbytes of memory and a 785) a while later.

Our current configuration boggs down heavily during the
afternoons and evenings, such that interactive response
time (especially noticeable for editing and mail) is
extremely poor. 

We are currently debating which of two solutions is
most likely to give us the most relief from this
problem.  One is to split the users evenly (load-wise)
between the two machines.  The other is to off-load the
non-interactive processes (text processing,
communication with the outside world, systems compiles,
VLSI design batch jobs (simulations and rules checking, for
example) to the larger of the machines and to keep all
'home' logins on the smaller machine.

I'd appreciate opinions, particularly if you have had
experience using a UNIX system as a 'back-end' machine
for CPU-intensive, non-interactive jobs.