Hi,
I am interested, if someone knows the difficulties to setup a huge LTSP, what means several hundreds of clients.
There are folks who organize large LTSP groups on fairs in the USA, read the articles on the ltsp homepage. My experience reaches up to a classroom of 24 clients, but there's a lot of things you can calculate from such an environment.
- Where are the biggest problems?
I would say, network and server load (mainly RAM)
- How much KDE-clients can i use performantly per server doing office/internet-jobs?
Well... that depends on your server and network... There are figures that say 100 MB per client. Up to now, I found that's pretty heavy, but it may depend on the kind of apps the clients are running, too.
- What type of server for this amount?
I'm running a double-Xeon system because you then have 4 processors that can share the load. If there's one process running wild it won't block the rest, load is spread perfectly on the four CPUs under Linux. 2 GB RAM give enough space for that amount of clients. If not, there is a certain swap space, but I didn't need that up to now.
- Do the different servers(kdm/gdm/xfs) work reliable in big clusters?
I've heard problems about kdm, so I took xdm - it doesn't look that fine, but a nice background picture will do a good job :-)
- How good does distributing of sound work REALLY?
There have been a lot of threads here about problems with sound, so I didn't try that. You can, however, easily calculate how much this will increase network load!
- What about network bandwidth?
The biggest load is when clients boot (loading the kernel and building up X11). After that, there is a smooth, relatively even network load that can be easily handled by any network. In my case, there is a limit of about 6 clients booting at a time. If you switch on many of them at the same time or one shortly after another (going through the room and pressing the buttons), the whole thing will hang after a while, then recover, and the last client will come up after about 10 minutes.
I have to add that my network has been "upgraded" from a simple BNC network with 12 clients to a bigger TP one with 24 clients by combining every 2 or 4 clients on a 10 MBit hub with a single line to the switch, so there are islands of groups of simple 10 MBit clients connecting to a 100 MBit switch which is connected to the server. You have to keep in mind that 10 MBit LAN cards have only half-duplex.
If you consider a "real" network with clients all connected to a switch by a 100 MBit line on there own (usually full duplex), there should be less problems :-)
- Smallest Client (CPU, Memory)?
I have a mixture of old P1 and PII clients with RAM from 16 MB upwards. Most of them have Matrox Millenium II cards with 2 MB RAM, some have bigger ones. RAM seems to be kinda problem: I found that e. g. Mozilla crashes the X connection if there's too few RAM - but 64 MB is enough anyway. If there are problems, I enable NFS swapping, that works perfectly.
Hope that gives you an idea...
Rolf
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