Killer Micro Question

[Mark Levison]

In article <16364 at s.ms.uky.edu> randy at ms.uky.edu (Randy Appleton) writes:
>I have been wondering how hard it would be to set up several
>of the new fast workstations as one big Mainframe.  For instance,
>imagine some SPARCstations/DECstations set up in a row, and called
>compute servers.  Each one could handle several users editing/compiling/
>debugging on glass TTY's, or maybe one user running X.
>

    We run just such a system in the Computing Science dept at Queen's. We
have a network of about 60+ sun3's and 6 file servers.  3 of the sun3's
(160's I think) act as terminal servers for the the people who do not have
workstations.  Each terminal has a simple modem which talks to a very primitive
login server that login server decides which machine hand you off to.  The
mechanism for deciding which machine to use is based either on the number of
ports in use or on a strict alternation scheme ie user 1 -> machine1,
user 2 -> machine 2, ..., user 4 -> machine 1.  This simple approach works
suprisingly well until several users who use use large amounts of CPU time
get logged on to the same machine.  Even a front end system that checks the
load averages of the machines breaks down here because the user who normally
uses a large chunk of the CPU time may be involved in a long edit phase or
maybe reading news :-)  The obvious answer is the operating system to perform
load balancing through process migration.  Hmmmm I wonder when Sun is going
offer us process migration (before anyone flames me there a probably a whole
host of subtleties I am missing here).

Mark Levison
levisonm at qucis.queensu.ca