[Server-devel] Latest on capacity of the school server

[Sridhar Dhanapalan]

On 2 July 2010 03:45, David Leeming <david at leeming-consulting.com> wrote:
> Hi from a small island in the north Pacific – Kosrae (FSM). Here they are
> going for a complete programme with all graders 1 to 8 . That takes in six
> Elementary Schools (the US system is used here) the largest has 3 streams,
> 24 classes and about 500 students. The school is arranged in a large U plan
> form in two floors/storeys.
>
>
>
> What experience do we have on the latest thinking about the capacity of a
> single server? Here in Kosrae they have good 24/7 power availability and
> air-conditioned offices in five of the schools. We can therefore specify
> powerful machines, even dedicated server models if need be.  If we segregate
> off each of the 24 class groups, would a single powerful machine server be
> able to handle 500 students in 24 classes (courses) simultaneously? (of
> course in practice that maximum load will rarely occur).
>
>
>
> I suspect we don’t have a definitive answer and I would like to develop a
> strategy with the ICT people here. Perhaps to plan for multiple servers in
> such a school and then progressively introduce them in response to the way
> they perform.
>
>
>
> Any feedback on good techniques or references/guidance on the wireless
> infrastructure would also be appreciated. In the larger school, we have two
> floors, 12 classrooms per floor, in U-shape layout. I would place one AP per
> classroom spread evenly around the school – that would be about 20 students
> per AP. The APs set up all on eth1 LAN with the same SSID. If we use
> multiple servers, we’d use different SSIDs for each. I have not deployed
> such a large site before so any comments on this would be appreciated.
>
>
>
> (2)
>
>
>
> In PNG SDP’s project in North Fly, PNG, we are using small “eboxes” because
> of the need to run on solar power. We have deployed one full-campus
> wireless/server installation, quite a small school (160 total, 80 users in
> the first roll out). These users are divided into 3 class groups, as Moodle
> courses. So they are segregated. We have had feedback that it still gets
> slow / congested when all users are on simultaneously (80 users in 3
> separate courses). I don’t have an opportunity to visit the school and
> quickly inspect the servers logs etc, so I am not sure of the cauase, i.e.
> the small capacity of the “ebox” or other cause. Any comments as to what to
> check would be appreciated

Here are the guidelines we are using in Australia with the OLPC
Australia variant of the XS.

1) 2-20 XOs should be able function using ad-hoc networking without
having a XS or AP present. An AP will allow for Internet access. There
is no real benefit in having an XS, from an architecture/scalability
perspective.

2) 10-30 XOs: 1 AP. An XS with a minimum of 1GB ram and 1GHz CPU is optional.

3) 30-60 XOs: 2 APs and XS with a minimum of 1GB ram and 1GHz CPU. You
may be able to get away with omitting an XS.

4) 60-100 XOs: 2-3 APs, XS with 2GB ram and 1GHz+ CPU.

5) 100-250 XOs: 3-8 APs, XS with dual-core 2GHz CPU, 2GB RAM. I'd
start to look at having gigabit connections between the XS and the
network switch that has the AP hooked into it. RF channel spread
between adjacent APs becomes the main site issue at this point.

6) 250-500 XOs: 5-15 APs, XS with dual-core 2GHz+ CPU and 4GB RAM,
gigabit network. Site issues will be the primary concern.


We have reckoned for 30 active XOs per AP.

XO-1.5 units support WPA2 encryption, but care must be taken with
XO-1s as they work best on open networks. Mixed 1.0/1.1/1.5 networks
may have to be left open.

Regards,
Sridhar


Sridhar Dhanapalan
Technical Manager
One Laptop per Child (OLPC) Australia
p: +61 425 239 701
w: http://laptop.org.au