I thank the community at Debian-Edu for the development and support as we are progressing towards free/open source software.
I don't know if my question is silly or off topic but,
We used to use a quad core CPU, 4GB RAM (i386 kernel), gigabit network, XFCE, debian (not edu) squeeze and pure LTSP thin clients without localapps in my institute. It served 30 to 35 clients (some with 512 MB RAM and even some PI systems also) surfing with iceweasel and using Openoffice etc with no apparent sluggishness.
Now upto a month back we had a dual core CPU (H61 board), 4GB RAM (i386 kernel), gigabit network having debian-edu wheezy main server+workstation+thin client server (no windows machine logging onto tjener) comfortably serving 15 thin clients with no glitches in UI while using XFCE. Students were comfortably using it for programming, surfing etc.
Now we have migrated to a new HP ML10 V2 server having Xeon E3-1220 V2 - 4 cores (amd64 kernel) with 8GB RAM in place of above machine. But, even with 5 thin clients, we are experiencing few (not too much) glitches in UI response. They appear on the main server also. Previous machine did not have this problem.
Possible reasons as I thought:
The server is running amd64 kernel while most clients run i686 (when seen by uname -a after logging in through tty on client) even though they all have 64 bit CPUs
The xeon processor has no graphics while the previous machine used as server had it. While serving the thin clients, if the graphics processing is being done on tjener, that might be a problem.
Can I use a graphics card on the server to overcome the problem if this is the reason? I don't want to use another machine for ltsp server as the clients would be at most 20.