[Server-devel] location and muscle of the school server

[John Watlington]

On Feb 19, 2008, at 9:28 PM, Sameer Verma wrote:

> I've been reading up on the specs for running the XS (XSX - the one  
> that
> relies on off-the-shelf parts) and one thing that keeps bugging me is
> that if we don't have reliable power infrastructure on site (which is
> why XO makes a lot of sense) how can we expect to run a
> common-off-the-shelf server that consumes 200W of power?

We don't.   Unfortunately, real world resource constraints impose
themselves --- OLPC doesn't have the resources to develop the
server hardware until later this year.   In the meantime, software
development can proceed using available hardware.

The off-the-shelf hardware that I'm currently testing uses 18 to 22W,
including the disk drive and three active antenna.
Not quite the 200W you cite...

There are schools that do have power, and are large/dense enough that
they need a traditional access point deployment.   These schools
WILL deploy with off-the-shelf hardware.

The reason to build an OLPC server is mainly environmental and cost.
Any server designed to run in harsh environments (temperature, dust,
and corrosion) is currently very expensive.   We can also drop the
power dissipation even more by moving away from x86.

> I see in the specs that the model of using an XO with external  
> drive as
> a school server is an option, but I wonder how far that has been
> explored. It is a great idea (after all, all nodes on a mesh are just
> that - nodes) but given the current development, it doesn't look  
> like an
> XO has enough to run Squid, etc. I take it that the current run of  
> XS is
> short-term?

The XO doesn't have enough memory to be a school server, and
the external disk drive needed is difficult to power from the  
internal battery.
We are still exploring our options here.

> Another point that came up a couple of days ago (when I was discussing
> this with a colleague) is why can't the server be further upstream  
> at a
> data center where it has adequate power and cooling?

Because less schools have internet access than power.  And if they
do have internet access, it is a few Mbits/sec.    Local storage is
critical to providing a decent user experience.

Think about you just proposed.   You want a hundred students to all
simultaneously try to download a 2 MB PDF over a 2 Mb/s line ?

Yes, there will be servers farther upstream, in nice cooled rooms,
providing additional storage backup and content/applications.  But
content used by the school must be cached locally to minimize
access latency.

wad