[ok-mail] [K12OSN] network design

[Les Mikesell]

On Sat, 2005-02-05 at 07:55, Sharon Betts wrote:
> Hi John,
> 	I am very familiar with K12LTSP (running a pilot in one grade now). 
> However, I do not need all the programs that come with the package -- also
> prefer to boot the terminals locally.   My request here is for some bigger
> thinking -- I wasn't very clear.   Should I put a server in each building
> (5) -- at each level or for specific applications?   How many connections
> can a server handle (remember I have 3000 users)?   What is the best way
> to handle authentication and/or DHCP?   We do use Star Office (free to
> education now) across the district as well as many other OS apps.

First you need to decide whether you want to optimize for easy
administration or bandwidth needs.  If you already have a gig
backbone everywhere you can ignore bandwidth - otherwise it will
be a problem unless you pay attention to topology.  Likewise if
you distribute the servers so the bandwidth use is local you can
make it difficult to manage. So, you'll probably end up making
some compromises.  Using a 2-NIC server per classroom/lab
can be done with no bandwidth-scaling problems and inexpensive
switches with 1 or 2 gig uplinks for the server connection.
You can make this easier to manage with a central authentication
server and a home directory server that all the classroom
servers mount via NFS.  This can be made more secure if you
can arrange for a separate isolated subnet just for the server
to server connections.  With an authentication and home directory
server, the local k12ltsp servers need nothing unique except their
'outside' IP address, so if you can get as much identical equipment
as possible you can roll them out by copying the whole drives. If
you get front-swap disk carriers and a few spare machines anyone
can fix any problem with the local servers by swapping in a new
drive or moving the old drives to one of the spare boxes (i.e.
most of the things that people would use to justify needing to
centralize the servers...) and you can do wholesale upgrades
with the ability to back them out instantly by cloning drives
and swapping them into the production servers.  You need to
apply the same reasoning to how much you centralize across
buildings.  You might compromise on central but replicated
authentication with home directories local to buildings and
a central backup mechanism (hey, another chance to plug
backuppc...).

-- 
  Les Mikesell
    les at futuresource.com