Advice on getting a computer lab server

[Kemp, Levi]

> -----Original Message-----
> From: edubuntu-users-bounces at lists.ubuntu.com 
> [mailto:edubuntu-users-bounces at lists.ubuntu.com] On Behalf Of 
> Gavin McCullagh
> Sent: Friday, January 11, 2008 8:40 AM
> To: edubuntu-users at lists.ubuntu.com
> Subject: Re: Advice on getting a computer lab server
> 
> Hi,
> 
> On Thu, 10 Jan 2008, Joseph Hartman wrote:
> 
> > I actually started rolling out an edubuntu lab earlier this 
> year and 
> > it became painfully clear early on that the server I have 
> (3.0 GHz P4 
> > Dell with 4GB Dual Channel DDR RAM) was not going to be adequate to 
> > handle all the thin clients.
> 
> How many was that?  I had understood from documentation that 
> you should be able to get up to 25-30 with that.
> 
> > I have since dedicated my efforts towards setting up 
> MiniLANs in each 
> > teacher's classroom with the P4 servers handling just 3 to 6 thin 
> > clients. This seems to be working alright, although things 
> are still 
> > pretty slow.
> 
> Another thing to consider is the disks.  IDE disks and 
> controllers are pretty poor for multiple user access.  If 
> you're going to have many users, SCSI is generally the way 
> forward.  3-6 should probably be okay with IDE I would have 
> thought and with a Pentium 4 running openoffice/firefox.  You 
> should perhaps try to check if the problem is lack of memory 
> or cpu on the server.  Highly animated applications like 
> tuxtype, tuxmath, et al, gcompris, video will cause video 
> slowdowns which could be your problem.
> 

I've heard of a few people getting away with SATA as a cheaper
alternative to SCSI. It will perform better than IDE, but it's still
going to be no where near as good as a SCSI setup.

> > I was hoping to use Kino and Blender with the middle 
> schoolers at some 
> > point in the future, but it isn't a big deal to postpone 
> those plans if need be.
> 
> Intensive video stuff sounds like something which might not work well.
> 
> > In my current lab if I try to run more than about 7 thin 
> clients they 
> > freeze up just playing flash games or running tuxtyping.
> 
> These applications could indicate network bandwidth troubles, 
> particularly if they all share, say a cheap 100Mbit hub.  
> 

I would have to concur. I don't think a 100Mbit connection to the server
is adequate, because you'd have to think that each of you clients would
only have 10Mbits to use. I'd suggest getting a cheap gigabit card for a
server to try but coming up with a switch with gigabit would prove more
difficult.

> There have also been reports of tuxtype and tuxmath crashing 
> thin clients so perhaps that problem is affecting you (one 
> which might not go away with bigger hardware).  Seemingly 
> turning sound off on the client can remedy this issue (I'm 
> not saying that's the answer, but it might help you identify 
> the problem).
> 
> > Like I said, I have 4GB of Dual Channel DDR RAM so is the 
> bottleneck 
> > with my 10/100 switch or my P4 CPU? Until now I've thought 
> it was the 
> > CPU because when I look at the system monitor the CPU maxes 
> out pretty quick.
> > (maybe I should bring my c2d in from home and try it out to 
> see how it 
> > holds up)
> 
> I'm afraid it's hard to pinpoint from here.  You need to look 
> at ways to measure RAM used (the output of the "free" command 
> is a start) and cpu load ("uptime" and "top").  If you have 
> some way to measure network load that would also be 
> interesting to see.
> 
> Munin is a very useful thing for monitoring usage of 
> bandwidth, disk, cpu load, ram usage, etc.
> 
> http://www.debian-administration.org/articles/229
> http://www.howtoforge.com/server_monitoring_monit_munin
> 
> > If I want to use the above programs and keep my current curriculum 
> > will a single server with 2 dual core xeons and 8 GB RAM be fast or 
> > just adequate?  I want the lab to be fast. (obviously I'm 
> just asking 
> > your opinion here)
> 
> If the lab is 30-35 users I would hope so but our usage tends 
> to be more sporadic so I don't have enough experience to be 
> sure.  A couple of other large installs (Jim K has 70 thin 
> clients?) have used several bonded Gigabit interfaces in 
> order to give the server >1Gb/sec access to the network.
> 

Our lab functions well with 2 xeons and 3.2gig of ram (32bit) and we
have had 30 students at once on firefox w/ flash, openoffice, and
whatever games they can find under he edutainment. They can even all use
reading counts running on flash. We don't do any heavy video graphics
stuff like blender so I can't say there.

> > Finally, what kind of switch should I get? Should I go all 
> gigabit or 
> > is it enough to just be gigabit to the server and 10/100 to the 
> > clients? I do a lot of flash based reading games and stuff with the 
> > lower grades like starfall.com and so I absolutely must 
> have these activities perform well.
> 
> The server really should have at least one gigabit interface. 
>  Limiting each client to 100Mb/s is perhaps not a bad thing 
> as it stops a rogue client from saturating the server's 
> network card and in principal leaves the other 900Mb/s for 
> other clients.
> 
> Gavin
> 
> 
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