ltsp server cluster setup

[Gavin McCullagh]

Hi,

On Sat, 28 Apr 2007, Tim Salcedo wrote:

> I'm new to Edubuntu and Linux but it looks like it's just what we need
> for our small school computer lab.  We have about 20 IBM 300pl machines
> with 256 MB of RAM and I would like to "cluster" 5 of them together to
> make a server and use the remaining for a 15 computer thin client lab.

Those are reasonable spec machines (~500Mhz cpu? 256MB RAM) for running
edubuntu desktops, though they're a little short for a server.  As Scott
says, if at all possible, you would be better off making one server
purchase to power the 20 thin clients.

Clustering in the way you seem to be suggesting (5 machines transparently
working as one server) is perhaps not impossible, but definitely a
difficult thing to do reliably.  I'd be inclined to steer clear of it.

What is your priority in doing this?  Is it low maintenance, simplicity,
low cost, technical fun, etc?  I can think of a few ways to go about it:

1. Buy one single powerful server and run all 20 thin clients off it.

2. Several little clusters of one server + two thin clients, all three of
   which provide a login.  

3. Run every client as a diskless workstation (fat client), such that the
   programs run on the desktops themselves but all disk storage and
   software installation is centralised to one place.

To my mind, [1] is by far the simplest, least maintenance and most reliable
route -- it's what edubuntu is designed for.  It has a cost though.  [2]
probably involves installing onto 5-6 machines as servers, maintaining the
installs and organising centralised storage and authentication.  [3]
still involves a little tinkering with ltsp, though I believe it's probably
not too bad now.  

Both [2] and [3] would still require one large, fast, reliable central
storage disk (ie not the kind in your IBM 300pl pcs) which almost implies
getting a server for the job.  You can probably get around this by
spreading home directories out over the small servers but really, you're
just inviting headaches.

> Is this possible using just edubuntu or is other software involved?
> Also, if this is possible, are there step-by-step instructions for how to
> proceed?

This stuff is all possible, but may not be that practical in reality.
Eur1500-1900 for a server might seem like a lot, but if it saves you
countless hours of administration/troubleshooting and gives you 20 reliable
working desktops, maybe it's not so much per desktop.  Depending on the
server you get, you could actually run more thin clients off it.

Gavin