Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!watmath!clyde!cbatt!cbosgd!ulysses!ucbvax!sdcsvax!darrell
From: darrell@sdcsvax.UUCP
Newsgroups: mod.os
Subject: Submission for mod-os
Message-ID: <2696@sdcsvax.UCSD.EDU>
Date: Tue, 10-Feb-87 20:56:24 EST
Article-I.D.: sdcsvax.2696
Posted: Tue Feb 10 20:56:24 1987
Date-Received: Thu, 12-Feb-87 02:00:20 EST
Sender: darrell@sdcsvax.UCSD.EDU
Organization: NASA Ames Research Center, Mountain View, CA
Lines: 32
Approved: mod-os@sdcsvax.uucp

One of Gene's throwaway lines seems to me to be a key point.  The idea
behind a lot of distributed systems seems to be that you could load balance
and gain fault tolerance by distributing. Unfortunately, you can do both
easier by using a multiprocessor, rather than a distributed system.

The NAS project here at Ames has taken an approach to heterogeneous systems
which is short of a distributed system.  We are taking work stations,
minis, mainframes, and supercomputers and building a computer system around
"a common user interface" by having them all run Un*x variants

This system isn't distributed, because the indvidual system's are autonomous,
but it allows much code to be easily transportable, and it allows us to
develop distributed applications.  And the results we are seeing are
reinforcing something I believed before I got here:  distributed heterogeneous
systems don't work because by being heterogeneous they prevent you from being
able to load balance and be fault tolerant.

This isn't suprising;  If the Cray 2 is down for two hours, there isn't enough
time on all of our stations combined to make up for the lost CPU cycles and
besides, the binaries won't run on a 68K anyway.

To me the answer is to run the machines with seperate operating systems, but
to provide user and programmer interfaces with good communications primitives
so that distributed applications can be developed.

I believe that the relative cost of communications versus multiprocessors
is always going to make multiprocessors more atractive for homogenous
applications than distributed systems and that the difficulty of programming
hetrogenous systems is always going to make autonomous systems more attractive
than distributed homogenous systems.

BTW Gene, aren't you ashamed to be badly plagerizing Einstein?