[K12OSN] Recommended Server for 25 terminals on K12LTSP 4

Owen O Donovan odonovan at bsd.sk.ca
Thu Oct 28 04:07:56 UTC 2004

As some previous writers have mentioned: it all depends on how many people are
doing what. (and mostly on 3 variables: cpu, mem and disk) 

CPU: I've seen acceptable performance for 15 people on a Celeron 300 --as long
as they are doing simple tasks with appropriate tools like basic text editing
and simple (non-animated) browsing. Somewhere between 50 - 100MHz/user is
where we seem to have landed. (One common config is a 2X~3GHz machine which
fast enough for most applications for around 60 users and puts it at the high
end of the range).  So 20 users implies about  1 - 2 GHz  (Hyperthreading &
multi procs are VERY helpful as they mitigate the effects of runaway
processes).--So your machine degrades gracefully under pressure.--  The 100MHz
per user figure lets a fair proportion of the clients use  Java, JavaScript &
Flash concurrently (in for example animated web pages)-- and play gazmes.  But
don't expect everyone to be able to do concurrent real-time video  without a
big boost in CPU specs (and some serious planning arithmetic beforehand)
Network considerations (more that a couple of 100Mbps NICS) also would come
into play.

Memory:  It's simple arithmetic again.  Open/Star Office often seems to take
from 50 - 70MB per instance (often less and sometimes more). Moz takes less
usu 25 - 50MB.  The key is to make sure you have enough RAM for the projected
users & usage to keep the system out of swap.  Extra mem is also important to
buffer you from the effects lost processes & runaways that are not properly
returned to the system when things go wrong. --grace under pressure again. 
For 20 users 1.5GB minimum; 2GB should cover you well.

Disk:  In most our schools, the Lbox just runs the applications and the file
service is done through nfs to a school-wide file server/authenticator/dhcp
server.The LTSP box just does tftp & nfs of the client files. If your setup
were like that and if you can keep the system out of swap, you can get away
with minimal disk resources (ie. 1 scsi).  The dual 3GHz macines ref'd above
have only 1 SCSI drive  & can run 60 users. But when we had them with 3G RAM
they ran out of mem at about 40 users. Then things really slowed down as the
machine went to swap on disk! An extra gig solved that. 

If you expect the machine to go to disk often (is it doing its own user file
service, print service squid caching; are you intentionally letting user
processes swap out; does it do dhcp, tftp, nfs for the terminals; are you
using a vm like VMWare or Netraverse; are you GIMPing larger images; ...) then
you need _minimally_ 2 drives.  Even in small schools (<10 terminals) we use a
2 drive setup for reundancy --performance is a side benefit.  Our experience
with IDE is that it's always unacceptable! (has anyone used it for class-sized
installations?)  SCSI works; I can't speak to SATA but would propose that you
consider more drives (>2)if you think of moving in that direction and perhaps
a small boost in CPU to offset the added load..

Good luck!


Owen O'Donovan
Battlefords School Division #118
(ph) (306) 937 7702
(fx) (306) 937 7721

Open WebMail Project (http://openwebmail.org)

On Wed, 27 Oct 2004 14:40:45 -0700, Huck wrote
> on my first test machine I used a P4 2.6 ghz with 2gig of ram...
> slow start up...but after start up everything was smooth....20 client
> machines
> --Huck
> Karolow, Mike [ITS] wrote:
> >If it's the type of situation where all 25 machines are going to log on
> >at once, like in a lab where all the students sit down and fire up the
> >machines together, I think there would be some *serious* lag there. Once
> >everyone's going, then you'd be fine. I'm running just a few machines
> >from a P-III 700 and load times are rough, so with 25 even on a faster
> >processor...
> >
> >Mike Karolow
> >Volunteer IT Administrator
> >the greenhouse school
> >Salem, Ma, USA
> >
> >------------------------------
> >
> >Huck wrote:
> >
> >If you wanna do it on the cheap(not looking for growth)...
> >
> >Grab an AMD 2000+ chip with about 3 gigs of ram...
> >40 gig hd if ppl aren't saving too much stuff to the server...
> >the gigabit ethernet is very helpful...
> >
> >and that'll hold ya quite easily...
> >
> >--Huck
> >
> >Wayne Fulton wrote:
> >
> >
> >
> >>We are looking into setting up a K12LTSP lab with 25
> >>workstations. What type of server minimal specs (memory, hard
> >>drive, scsi or ide, processor) do you recommend?
> >>
> >>Thanks!
> >>Wayne
> >>
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