Re: [school-discuss] linux distributions for low resource computers,

[Dean Montgomery <dmonty@xxxxxxxxxx>]

On June 3, 2008, James P. Kinney III wrote:
> Can you provide some specs on the server you are using? My LTSP servers
> are pretty beefy monsters (2-4 cores, 2-4 CPU's, 8+GB RAM, multiple Gbit
> NICs, etc) that run 100-150 thin clients each.

That is in the ballpark that we have been using.  Spend money on the server and save on the client.

With LTSP when we loaded up a lab of 30 students doing Java games, youtube,  or trying to do any 3d accelerated programs the server and the network would bog down.  Even powerpoint slide transitions are choppy on LTSP.

With diskless once the java game (or google earth) is loaded, there is no more network traffic.  A bonus is the kernel caches the program in the client's ram so the next time openoffice or firefox is clicked on, it starts almost instantly with very low network traffic.   We can have 100+ kids and teachers doing a java game, youtube, openoffice, or google earth without any performance issues.


> I would expect for 
> diskless clients the key factors will be primarily network bandwidth
> followed by hard drive throughput.

That is why we do a gig connection from the server to the switch.  Hard drive is a RAID - kernel does some file caching so the drive isn't thrashing.  Using sar I've noticed that the nightly backup is the only time that the hard drive and CPU start pushing 100%.  Throughout the day they rarely reach 100%.

> The main reason I have been avoiding the diskless format is heat and the
> need for fans. A silent environment is a big plus from the thin client
> format. Although I do have my hands on a new fanless client from VIA
> (pico-format) that can be either diskless or thin format.

Yes I agree.   We have been focusing on cost savings instead of noise reduction.  The computers are quieter than fat clients but they still have a CPU and Power fan.  AMD's Cool-n-quiet throttles it down even more.


Here is a screenshot of a diskless desktop...
http://www.sd73.bc.ca/misc/linux/sd73.png
... and yes all the students can do this at the same time with no slow-downs or lags. : )  Think about it... the movie file is travelling over the network as compressed avi and then is decrypted/displayed on the client workstation.  Beryl is loaded into client RAM and doesn't require much network IO.

Here is a screenshot from on the server running about 150 diskless clients.  Notice the gkrellm monitor on the left showing 46% & 10% cpu usage; bond0 is 2 bonded NICS.  MEM is hardly being used.
http://www.sd73.bc.ca/misc/linux/skss_charts.png

The rest of the screen shots are from sar and they show that the biggest load on the server is during the nightly backups.
http://www.sd73.bc.ca/misc/linux/

====
If you still don't believe me see what Robert Arkiletain says about diskless.  (Robert wrote Teacher Tool for LTSP.)

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