[K12OSN] Where is the bottleneck?

CLIFFORD ILKAY clifford_ilkay at dinamis.com
Wed Jul 28 01:12:16 UTC 2010

On 07/27/2010 08:20 PM, Christian Einfeldt wrote:
> Hi
> I have been supporting public schools w LTSP and LDAP for 6 years (about
> to start the 7th year). For the first three years, we ran LTSP.  At the
> beginning of the 4th year, we went to LDAP for exactly the reasons you
> cite here, namely lagging across the network.  I am only a level one sys
> admin (I'm actually a lawyer in my day job), but I'm pretty sure the
> real sys admins chose LDAP because it was more efficient to push some of
> the load onto the clients rather than have the dervers bear so much of
> the brunt.

LDAP wouldn't make any difference in video performance. It's purpose is 
centralized authentication.

The machine on which I'm typing this is an i5-750 with 4GB of RAM and an 
nVidia 9800GTS video card running Fedora 12. Firefox and Flash are quite 
piggy so especially if I have a bunch of tabs open in Firefox, I can 
notice degradation in video playback performance. Higher resolutions 
only exacerbate the problem. If this is an issue on a reasonably fast 
machine like the machine I'm using where data doesn't have to traverse a 
network, you can imagine that once packets have to be pushed across a 
network, even if it's a Gigabit network, you'll have problems. In fact, 
a handful of thin-clients playing a YouTube video will bring even a fast 
server to its knees, if the network isn't saturated first. At the school 
at which I volunteer, the school administration was complaining loudly 
one day when anything they attempted to do on the network, such as 
accessing the file server or checking email, would take intolerably long 
and in some cases, time out. I checked the mrtg graphs for the day in 
question and saw two spikes in network traffic, one in the morning and 
another in the afternoon and asked the IT Coordinator to find out what 
was going on at those times. Apparently, a few of the teachers were 
streaming FIFA World Cup games over the Internet and that was enough to 
saturate the Gigabit network to the point where other network services 
were adversely affected.

The solution to the original poster's problem is apparently specifying 
that certain apps, like Firefox, should run locally on the thin-client. 
I've only read about it and haven't done it so you'll have to do your 
own tests to confirm.

Clifford Ilkay
1419-3266 Yonge St.
Toronto, ON
Canada  M4N 3P6

+1 416-410-3326

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