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Old 01-10-2008, 03:31 PM
"Kemp, Levi"
 
Default winbind use default domain

Can anyone think of a reason why winbind use default domain = yes would stop working? Before they could log in with usersname/password, but now it is domain+username/password.

Levi Kemp
Technology Specialist
Bolivar R-1 Schools
417-328-8943
lnkemp@bolivar.k12.mo.us

"The only secure computer is one that's unplugged, locked in a safe, and buried 20 feet under the ground in a secret location... and I'm not even too sure about that one"

--Dennis Hughes, FBI



-----Original Message-----
From: edubuntu-users-bounces@lists.ubuntu.com on behalf of Gavin McCullagh
Sent: Thu 1/10/2008 3:35 AM
To: edubuntu-users@lists.ubuntu.com
Subject: Re: Advice on getting a computer lab server

Hi,

On Wed, 09 Jan 2008, Joseph Hartman wrote:

> I'm looking at purchasing a server for my school's multimedia lab to use
> with Edubuntu and LTSP. What are the minimum specs I should look for in a
> server that will power a lab with 35 P3 machines with 128MB RAM each? I
> teach elementary and middle school and

First of all, in case you haven't, I'd suggest you try Edubuntu out with
some existing hardware before you launch into buying lots of hardware. You
presumably already have the thin clients, so maybe find a Pentium 3/4
somewhere with 512MB RAM, install edubuntu, and try one or two thin clients
on it (actually 256MB might be enough for a test). This means that when
you're ordering your hardware, there are less unknowns.

> will need the machines to be able to do all kinds of multimedia from
> editing movies to creating flash files to streaming video from the
> Internet.

What software will you use for these tasks? Have you tried them out
already? There is video editing software for Edubuntu, but it's probably
not as well developed as some other aspects (and to be honest, it's not
close to Final Cut Pro in most reviews I've seen).

http://www.linux.com/articles/60837
http://www.linux.com/feature/60624

I know there are some ways to create flash, but have you checked that
they're right for what you want? It would be interesting to hear your
findings.

> Will two dual-core xeon processors do it for me or do I need to go quad
> core?

For normal applications like web browsing, office, image editing etc. the
quantity of RAM is usually the thing that limits the number of clients.
4GB RAM should probably cover 35 users for those applications. CPU doesn't
usually limit this sort of stuff.

I've never seen an edubuntu cluster with 32 people doing video editing at
the same time. If they were all editing even moderately large video
content, I'd say you could run into problems with both RAM and CPU.

The next issue will be video playback. If a thin client plays a full
screen video, it gets rendered (from say, divx) on the server and sent as
raw video across the network to the thin client. That's 2 or 3 bytes per
pixel, about 1 million pixels per frame, 24 times per second (ignoring
sound) all of which must be sent over the network from the server to the
client in real time. That's a LOT of network traffic. If more than 5-10
users simultaneously watch full screen video on normal thin clients, even a
gigabit network will be in trouble.

To be honest, for any sort of intensive video applications, traditional
thin clients are not really suitable as the network traffic is too large.
A few youtube videos here and there will probably be fine, but a class
doing video editing may not be not realistic. If the thin clients ran the
video applications locally themselves that would be different, but that's
quite complicated to do and your thin clients probably don't have enough
RAM.

> (Does Ubuntu even support quad core processors at this time?)

I'm pretty sure this is no problem at all. linux supports multiple cores
and multiple cpus and has done for a long time.

> How much RAM should I get and how much does Ubuntu support?

Default 32-bit edubuntu supports up to 4GB (this is a limit of 32-bit
hardware) and with the -server- kernel can get at least up to 8GB. 64-bit
edubuntu supports so much more, you won't be need to worry about it.

2^32 = 4294967296 =~ 4GB
2^64 = 18446744073709551616

> Should I just get 2 less powerful servers and split up the lab?
>
> I'd prefer to have one server so I can have some control over the lab using
> the thin client manager, but it isn't a huge deal. Thanks for any advice.

An interesting question -- there are advantages in both.

If you had two servers and one went down (eg. hardware failure), it would
be nice that everyone could move over and work on the other, even in a
limited way. This should be a rare occurance though.

Having, say 2x quad cores on one machine gives all users access to 8
cores. Having 2x dual cores on two machines splits your users in half
giving each half 4 cores. If you get a burst of use on one half, the other
half is not in a position to help out and could be sitting idle. Also,
you'll have to use NFS and LDAP or NIS to make all users able to login on
both machines and see their home directories.

Price will also vary between the two options of course. The single big
server would probably draw less power and use the same or less space.

Either way, look into getting RAID (preferably RAID1), so that a disk
failure doesn't take your server down and consider a second power supply so
that a failed psu won't take it down either. Remember if your server dies,
every thin client dies with it.

Sorry if some of this has set you back a little, but you must be realistic
about video applications on thin clients before you spend lots of money.

Gavin


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