My orginal question:
We are looking into setting a summer school Lab session and would like
to connect a number of X terminals on a couple of Alpha workstations
running MatLab.
Does anyone has any idea or experience on how many X terminals
an Alpha DEC 3000/400 system with 96 MB of memeory can reasonably
support? Any comment on experience for similar situations would
be most appreciated.
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Many thanks to all who replied giving me lots of good ideas of what to watch
out for. As a summary, the number varies from 6 to 20 depending on the
application. With MatLab, it is probably towards to lower end of the scale.
Here are the responses:
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From: "Bernt Christandl" <beb_at_rosat.mpe-garching.mpg.de>
Hi Shiu,
we have some 3000/400 and are running them with Xterminals only,
that is with a good old vt220 as console-terminal. We have 160 MB
of memory.
Our main application is an image-processing one (scientific investigations
of some sattelite image data).
We have experienced that with about 5 or 6 users working at the same time
they may have a "feeling of slowliness". That means their answers from the
3000/400 are slower then (sometimes remarkably) as when they work alone.
Hope this helps,
Bernt
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From: Steve Osselton <so_at_prismtech.co.uk>
Hi,
We run a number of DEC VXT 2000+ X-terminals from a dec 3000/800s. The
number that can be supported happily very much depends on what people tend to do
with their X-terms and the amount of physical memory on the Alpha. I encourage
people here to run their window manager and terminal session locally on the
X-term and simply connect through onto the Alpha. The Alpha performs well until
it's memory becomes exhausted and it starts to swap at which point there is a
noticable performance drop. If people intend to run mwm, gdb, xload, 6 dxterms
etc. on every X-term then obviously far fewer can be supported. The best way to
guess how many X-terms can be easily supported is to guess the average number of
processes run on the Alpha for each X-term and hence the Alpha memory
requirements for each X-term. The amount of free memory on the Alpha divided by
this number should give a ball park figure for the number of X-terms that can be
supported. Hope this helps.
Cheers,
Steve Osselton
steve_at_prismtech.co.uk
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From: Herve DEMARTHE (CEA France) <demarthe_at_alpha.cad.cea.fr>
Shiu,
we are also running MatLab on DecStations 3600 or AlphaServers 2100 4/275.
Users run Matlab from the console, from Macintoshes (with Versaterm Pro) and
from Tektronix XP 356 X terminals.
In our case (and probably your's) the problem is not the X-terminal but
Matlab ! (which is a heavy resource consumer).
Our X-terminals have 8 or 10 MBytes of memory, the 3600 have 96MB RAM and
512 Mbytes of swap area, we applied this formula :
32 MB system + ( 8 users x 8 MB ) = 96 MB
allowing 8 simultaneous MatLab users on a 3600
We improved things by running the Motif manager locally to the X-terminal.
We are installing 2100 multi-CPU servers with 128 MB per CPU and 1GB of swap.
We expect to support about 12 MatLab users per CPU on these servers.
Hope this helps, I think that in this case Matlab is the dimensioning factor,
+--------------------------------------------------------------+
From: William Flett <will_at_dcs.rhbnc.ac.uk>
This is a really tricky, how long is a piece of string question, but we have
running a 3000/400 with 64Mb of memory since the product was launched so
we have some idea. In our case we run approx. 20 NCD Xterminals (some with
local window managers) without too many performance problems. The crunch is
the nature of the work. If MatLab is memory intensive that'll be a probable
limitation, if it's disk intensive then spread the IO over different disks,
etc... Our work load is mainly sporadic and interactive in nature (approx.
40-60 logins shells) and a little CPU bound simulation. This combined with
384Mb of swap space spread over 4 disks works quite well. Occasionally we
do have a swapping mad 5 minutes, when a user starts every program under sun
on login so we do intend to upgrade memory to 96-128Mb this summer.
Rather a woolly answer to a difficult question but at least it gives you some
idea.
-Will
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From: Sid Fagan - Sublimation MAN (NID) <fagan_at_large.fnal.gov>
Don't know but the big question to how many it will support
is who is running the session manager. You might want to
rewrite the question. If the x-terminal runs it's own
session manager the amount it could server would be extreamly
high but otherwise the limit may fall short of expectations.
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Received on Tue May 16 1995 - 20:29:04 NZST