User story: Edubuntu lab running 43 clients --- needs some tuning

[Hendrik Boshoff]

To the Edubuntu-Devel mailing list:

Today was the first day of our new school year, and we had a server and
43 client machines running standard Edubuntu at the Laerskool Unika
(http://www.unika.virafrikaans.com/) in Johannesburg . The server is
brand new and fairly high end, and the clients quite old, mostly PII 266
MHz and Celeron 333 MHz with 64 MB of RAM. There was no instruction to
speak of, but the 7th grade children enjoyed the games and the novelty
immensely.

I am very excited about the possibilities of Edubuntu, and I want to
thank everyone involved in creating this environment. Unika's lab does
not have Internet connectivity yet (apart from a makeshift dial-up) but
the number of applications available in the Universe is mind boggling.

Our server has a dual Xeon 64 motherboard with CPUs running at 2800 MHz,
and 4GB ECC RAM. Hard disks are 3x 73 GB SCSI 10 000 rpm in a RAID5
configuration. The Gigabit network card connects to a 3Com switch with
24+2 ports (100 & 1000 Mbps). The other wideband port connects to a
second switch, and the 43 client machines all have 100 Mbps NICs.

The mixed group of 43 clients all boot fine, mostly using a stiffy
(regrettably, but it works) for the first phase. Four of them default to
640x480 screen resolution, which is below what I regard as the absolute
minimum of 800x600 for running Gnome.

I have been working *many* hours (with help from my children aged ten
and thirteen) during the last six weeks' holiday mainly to get the
hardware reconditioned, the various NICs to boot, and testing which
video cards would run X. It was nothing like the Edubuntu blurb claiming
an educator could get a lab up and running in an hour with donated
machines (http://wiki.edubuntu.org/EdubuntuWiki). I am proud to have
kept 75 machines out of the landfill however, having passed 35 working
P1 166 & 200 boxes on to another school. One current minimum for an
Edubuntu client seems to be 64 or 48 MB of RAM, although this may depend
on the video card. Has anyone managed to boot a client with only 32 MB?

Of course I want to get the maximum out of this setup, and it seems to
need some tuning. Can anyone suggest tools for finding the bottlenecks?

The lab has not really been given a stress test, but it easily supports
a class full of learners playing games. When OpenOffice Writer is
activated on only a single client, it takes about 10 seconds to load. If
ten clients try at the same time, it gets so slow that it seems to hang.

Looking at the system resources, the network seems far from saturation
at about 200-300 Mbps, and the memory far from used up at about 1.5 GB
out of the 3.5 GB available. However, the CPU bar often goes to 100%,
and stays there for long stretches.

So it would seem that the server CPU is the limiting factor. Firstly, we
are running the 32 bit version of Edubuntu software on a 64 bit CPU,
because of the mixed environment problem in Breezy. I am a bit wary of
running Flight 2 of the next release in a production environment. That
should improve after April. Secondly, I need to know whether the second
CPU is used at all. How can I find out?

What else can you suggest to speed things up? Lowering the colour depth
from 24 bit? Who has run an Edubuntu lab of roughly this size, and how
is it configured?

I still have use for some Edubuntu posters and other promotional
material. I am currently the only evangelist around here :-). At some
point I want to invite teachers from other schools to come and see what
can be done with old hardware.

I look forward to the live CD of Edubuntu, which I want to give to every
pupil in the school for home testing, and I would like to see a DVD
distribution with many more packages.

Thanks for any input.

Hendrik Boshoff
Associate Professor
Department of E&E Engineering
University of Johannesburg