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From: ian@sibyl.eleceng.ua.OZ (Ian Dall)
Newsgroups: comp.arch
Subject: Re: Single user vs. shared (was Re: Killer Micros and vectorized code)
Message-ID: <500@sibyl.eleceng.ua.OZ>
Date: 21 Mar 90 00:44:50 GMT
References: <51771@lll-winken.LLNL.GOV> <100598@convex.convex.com> <52661@lll-winken.LLNL.GOV> <1990Mar18.023523.4034@ultra.com> <52817@lll-winken.LLNL.GOV> <1990Mar19.220617.26370@world.std.com>
Reply-To: ian@sibyl.OZ (Ian Dall)
Organization: Engineering, Uni of Adelaide, Australia
Lines: 57

In article <1990Mar19.220617.26370@world.std.com> bzs@world.std.com (Barry Shein) writes:
>
>The argument is that because a personal computer/wkstn is idle 99% of
>the time therefore it would be better shared.
>
>The problem is that although this argument seems great in theory, in
>practice it tends to have real problems.
>
>When people share a computer things go wrong, the biggest thing that
>goes wrong is that one cannot estimate, day to day, what to expect
>from the shared computer.
>
>One day it can look up 1000 queries in an hour, the next day you only
>get 10 per hour (oops, someone out there is running a CPU hog.)

It is not just the mips which are being shared, it is also the code.
With a central machine you only have to find memory for your kernel,
emacs etc once. With N machines you have to find it N times. There are
significant technical advantages to a machine as has been already
pointed out to others.

Some people complained about not being able to run the software they
want on a shared machine, but I don't buy that.  So long as you have a
big enough disk quota you can run what you like.  If you don't have
the disk space buy more disks. I fail to see how attaching the disk
which would have gone with your workstation to the central machine can
not be a more effective way of getting the disk space for your
favorite application (at least you only need space for the extra
utilities, not the entire system). Instead of buying a workstation,
try offering to buy the central system a disk on the condition that
you are the only one with a quota on that disk.

The other problem seems to be that, sure people would like to be able
to use spare capacity, but they like to be guaranteed a certain
minimum number of cycles. Well, let me propose the guaranteed share
scheduler! I doubt if this is new but I'll propose it anyway!  Suppose
the total number of cycles per unit time is T, the maximum number of
users is M and the number of active users is A. Every user should get
max(T/A, T/M) cycles per unit time. The T/M is guaranteed, the T/A -
T/M is the bonus for being shared. Of course, for the convenience to
approach that of your own workstation you need T/M to be reasonably
large. One killer micro worth maybe?

The final problem is the fascist system manager. I don't know how many
of these there really are, I suspect that most are only trying to make
best use of too limited resources and that buying more resources is
the best solution. If you really do have a fascist system manager,
then sack them.

>Why do you think so many frantic hackers became night-owls?

Maybe because they want *more than* 1 workstation worth of cpu? On a
single user machine they don't have that option.

-- 
Ian Dall     life (n). A sexually transmitted disease which afflicts
                       some people more severely than others.