remote operation or admin

[Mike Meyer]

On Wed, 19 Mar 2008 21:33:11 +0100
Erik Trulsson <ertr1013 at student.uu.se> wrote:
> A system that is written to work in a clustered environment can fairly
> easily be moved to run on an SMP machine, but it will do a lot of work
> that is not necessary under SMP and thus not make very good use of the
> hardware.
> Moving from SMP to cluster is more difficult.  One can emulate the missing
> hardware support in software, but this has a very high overhead. Or one
> can rewrite the software completely, which is a lot of work.

One way to think of such is that cluster software will typically
consist of lots of processes talking to each other over sockets
whereas SMP software will typically consist of one process with
threads talking to each other through shared memory locations. On an
SMP system the cluster software could be rewritten to use shared
memory and hence improve performance. Likewise, moving the SMP program
into a cluster environment means you have to replace shared objects
with proxies that copy things around and coordinate actions.

At least one concurrent software development system (Bertrand Meyer's
SCOOP) is set up so the developer doesn't worry about those things;
the location and communications channels of the objects in the program
is specified at launch time.

   <mike
-- 
Mike Meyer <mwm at mired.org>		http://www.mired.org/consulting.html
Independent Network/Unix/Perforce consultant, email for more information.