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From: randy@ms.uky.edu (Randy Appleton)
Newsgroups: comp.arch,comp.unix.questions,comp.unix.wizards,comp.unix.admin,comp.unix.large,comp.unix.misc
Subject: Killer Micro Question
Message-ID: <16364@s.ms.uky.edu>
Date: 14 Nov 90 07:10:19 GMT
Reply-To: randy@ms.uky.edu (Randy Appleton)
Organization: U of Kentucky, Mathematical Sciences
Lines: 72

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.

But how does each user, who is about to log in, know which machine to
log into?  He ought to log into the one with the lowest load average, yet
without logging on cannot determine which one that is.

What would be nice is to have some software running at each machine, maybe
inside of rlogind or maybe not, that would take a login request, and check
to see if the current machine is the least loaded machine.  If so, accept
the login, else re-route it to that machine.

It would not be good to have each packet come in over the company ethernet, 
and then get sent back over the ethernet to the correct machine.  That would 
slow down the machine doing the re-sending, causes un-needed delays in the
turn-around, and clog the ethernet.

Also, all of these machines should mount the same files (over NSF or
some such thing), so as to presurve the illusion that this is one big
computer, and not just many small ones.  But still, it would be best 
to keep such packet sof the company net.

One solution that directs logins to the least loaded machine, and keeps
the network traffic shown to the outside world down, is this one:

   Company Ethernet
--------------------------+------------------------------
                          |         
                          |  ---------------
                          ---| Login Server|----   ----------
                             ---------------   |  | Server1 |
                                    |          |-------------
                                 -------       |   ----------
                                 | Disk|       |---| Server2 |
                                 ------        |   ----------
                                               |        .
                                               |        .
                                               |   ----------
                                               |--| Server N|
                                                  ----------

The idea is that as each person logs into the Login Server, their login 
shell is acually a process that looks for the least loaded Server, and 
rlogin's them to there.  This should distribute the load evenly 
(well, semi-evenly) on all the servers.  Also, the login server could have 
all the disks, and the others would mount them, so that no matter what node
you got (which ought to be invisible) you saw the same files.

The advantage is that this seup should be able to deliver a fair 
number of MIPS to a large number of users at very low cost.  Ten SPARC
servers results in a 100 MIPS machine (give or take) and at University
pricing, is only about $30,000 (plus disks).  Compare that to the price
of a comparabe sized IBM or DEC!

So my questions is, do you think this would work?  How well do you
think this would work?  Do you think the network delays would be
excessive?

-Thanks
-Randy

P.S. I've sent this to several groups, so feel free to edit the
'Newsgroups' line.  But please keep one of comp.arch or comp.unix.large,
cause I read those.
-- 
=============================================================================
My feelings on George Bush's promises:
	"You have just exceeded the gulibility threshold!"
============================================Randy@ms.uky.edu==================