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From: bzs@bu-cs.bu.EDU (Barry Shein)
Newsgroups: net.unix-wizards
Subject: Multiple Unix Universes
Message-ID: <2762@brl-smoke.ARPA>
Date: Sun, 3-Aug-86 12:36:37 EDT
Article-I.D.: brl-smok.2762
Posted: Sun Aug  3 12:36:37 1986
Date-Received: Mon, 4-Aug-86 00:58:28 EDT
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Re: Hypervisor, VM, run 'em both at once

My, my how things do transpire...

We could put up a system like this tomorrow on our IBM 3090, for example
putting up Amdahl's UTS and IX/370 under VM simultaneously, I have a
little feel for these things from a practical level (we run 3-4 O/S's
under our VM.)

In theory it's trivial to provide some way to choose which UNIX would get
bootstrapped at login (remember, on an IBM one logs into VM which then
would proceed to boot the O/S as part of the login process, or you'd
have dedicated ports that your MUX [or via distinguished phone hunt
groups] have divvied up.) Also note that booting something like UNIX
on a good sized [eg 3090] IBM probably takes as long as it takes you
to now get through tset etc [20Mips, FAST disk channels etc]. To choose
at login you'd probably just login in as 'loginname/ostype' or something
obvious like that.

Each would have to have its own mini-disks (virtual disk areas) as
4.2 and SYS/V currently use incompatible file system structures.
Further this means they could not share (mount) these disks any more
than you could mount a removable disk pack from the other system
in a conventional setting. If I really had to solve this I think
I would look at running NFS over a virtual IPC channel within the
machine.

Currently these various systems available utilize different terminal
hardware on IBMs basically owing to the problem that no IBM tty
hardware is suitable for full-duplex ascii terminals, so each
developer had to "make it up", Series/1, 4705 with mods etc.
This hurts any effort but the obvious solution is to use TCP/IP
and something like an Annex box (TCP/IP terminal server).

Of course, unless you have a good reason to do all this, this approach
is absurd, it would be more cost-effective (well, assuming that most
of your users use one system and a few need access to the other) to
just buy two boxes, for example I am typing at a SUN3/4.2 right now
and I could (and have) just ship any code I thought might need to be
tested for SYS/V compatability to the 7300 on my desk here.

Those folks who really need to run two APPLICATION environments (eg.
the word processor they *must* have only runs under SYS/V and the
database they *must* have only runs under 4.x) have worse problems.
Personally I would (and have) play systems fascist and tell them to go
choose compatible software or get out of my office (I mean, it ain't
just SYS/V vs 4.2, they'll pull that BS on you with AOS/VS, IBM/VM and
VMS also if you let them start squawking, hell, they can do whatever
they like, so long as they don't expect me to clean up the mess later
when they're sorry, or burden the extra costs.)

What is utterly absurd is the lengths to which people are going for
this compatibility, like an animal gnawing off its leg to get out
of a trap.

Obviously we need one O/S that is a superset of the two, and fast,
before this lunacy of dual universes and half our disks being taken up
with nearly unnecessary #ifdefs (well, I exaggerate) eats us alive.

Of course, when this mythical system hits the market it will cause
a period of pain due to certain mutually exclusive semantics of
the two systems (eg. a.out formats, signal semantics, some commands)
but I at least that changeover might well be the last, so at least
it would be worthwhile as an investment.

I know, P1003, but so far that's a document not a program, maybe
someday, and maybe if it incorporates enough of the parts of each
I feel I need. Until then I'll run 4.x (my preference) and try to
ignore all the other competitors in general.

Reading all these messages I am not sure whether to laugh or cry...

	-Barry Shein, Boston University