[Beowulf] help! need thoughts/recommendations quickly

Mike Eggleston mikee at mikee.ath.cx
Tue Mar 2 09:08:56 EST 2004

On Tue, 02 Mar 2004, Robert G. Brown wrote:

> On Tue, 2 Mar 2004, Mike Eggleston wrote:
> > I realize this question is not specific to beowulf clusters... however,
> > at 9a I'm meeting with an upset user about a bunch of workstations
> > using serial termainals. Things don't happen as quickly as he wants:
> > setup, problem diagnosis, throughput, etc. What solutions can I present
> > for these problems (I realize this is just a quick summary!). Also,
> > the serial terminals are running at 9600 baud over sometimes 50 meters.
> > One table I found shows 60 meters is 2400 baud and 30 meters is 4800
> > baud. I think this is part of the problem.
> It really shouldn't be, if the wiring is decent quality TP.  Back in the
> old days, when our department was basically NOTHING but serial terminals
> running over TP down to a Sun 110 with a serial port expansion, we had
> lots of runs over 50 meters (probably some close to 100) without
> difficulty at 9600 baud.  Keep the wires away from e.g. fluorescent
> lights (BIG problem), major power cables, or other sources of low
> frequency noise.  Running parallel to a noise source over a long
> distance is where most crosstalk occurs -- try to cross wires at right
> angles.  Conduit can help as it shields, as well, but our wires were
> basically thrown up in a drop ceiling haphazardly by "trained
> professionals" a.k.a. graduate students, faculty, and sometimes a
> shop/maintenance guy.

I know it should work and the old way it does work, but I've always
seen problems with serial and printers. I much prefer getting away
from them to full ethernet.

> > Possible solutions I have thought of:
> > 
> > - user stops complaining and deals with the situation
> Always a popular one.  To accomplish it you had better be prepared to
> use force.  Bring duct tape to the meeting...

This problem is happening in the warehouse, so there is lots of packing
material and tape around. :)

> > - put ethernet->serial converts at the terminals so the terminals are
> >   on the network
> Sounds expensive.  Of course, terminal servers themselves are typically
> pretty expensive, although we used to use them in the old days when we
> finally had more terminals than our server could manage even with
> expansions.  And then workstations started getting cheaper and we
> converted over to workstations and ethernet and never looked back.
> How is it that you're still using terminals?  I didn't know that
> terminals were still a viable option -- a cheap PC is less than what,
> $500 these days, and by the time you compare the cost of the terminal
> itself, the serial port terminal server, the serial wiring, and the
> incredible loss of productivity associated with using what amounts to a
> single, slow, tty interface they just don't sound cost effective.  Not
> to mention maintenance, user complaints, and your time...

This is an application in the warehouse. We have many serial (dumb)
terminals and printers. We are using 'Dorio's(?). Similiar to the
Wyse 60. I've not used a dorio before, but wyse terminals lots. The
application is all curses based and doesn't require much. The users
are not even concerned about the speed of the application (display, etc.)
just that the terminals are quick to setup and work all the time.

> > - put small VIA type boards whose image is loaded through tftp and
> >   the serial terminals actually run from the via boards
> > - what else?
> Give the terminals to somebody you don't like, replace them with cheap
> diskless second hand PCs on ethernet running a stripped linux that
> basically provides either the standard set of Alt-Fx tty's in
> non-graphical mode or basic X and as many xterms as memory permits.
> Problem solved.
> In fact, depending on the applications being accessed and whether they
> CAN run locally, problem solved even better by running them locally and
> reducing demand on the network and servers.

I can use the terminals on the via boards and not have to replace
them with crt monitors and keyboards, until they all start failing.
I'd prefer to use the crt monitors through vga (fewer problems with linux
and getty).

Do you (anyone) know of a cheap motherboard that would do this?

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