2.3. Thin Client Server

The function of this profile is further described in TODO Section 5.2

The most important, absolutely important thing is plenty of high quality ECC RAM.

• The amount of RAM you need depends on how many thin clients you have, and the pattern of use, see TODO the sidebar To-do. The rule of thumb says 64-124MB RAM on the thin client server for each thin client you have and about 256MB for the server itself. For about 40-50 thin clients 4GB of RAM is sufficient, which is also the maximum amount of RAM that a ready-compiled Linux kernel for Skolelinux/Debian-edu supports. See TODO Section 8.4 how to install a kernel with support for up to 4GB of RAM and multiprocessor(SMP). If you have more than 4GB of RAM in your server, then you must compile your own kernel with support for that. That is not (yet) the scope of this document, but the clue is to have in your kernel config file

  CONFIG_HIGHMEM64G=Y

• You definitely want to have two processors, that way one user can start a heavy process, such as Gimp, and lock up one CPU, and there will still be one easily available for the other users on the system. It's not crucial to have the fastest CPU available on the market, having two is more important.

• On a machine with the thin client server profile installed, no user data or home directories will be saved. All user data will be NFS-mounted from the machine with the profile main server. There is no need for a large disk on this machine, unless you choose to also use it as an external backup machine, see TODO the sidebar To-do. A 9GB disk is enough for such a machine, but it should be SCSI, because of the heavy load with many thin clients.

• You must have two network cards, of good quality. One card (eth0) will connect to the main server to get home directories; the other (eth1) will connect to the thin-client switch, this card should have 1000mbit speed, and the switch should have a 1000mbit uplink port.

Remember that each thin client uses about 2Mbit of network bandwidth, which means that on a 100Mbit network, you can't have more than about 50 thin clients. If you need more than that, you must get more thin client servers, or invest in a 1Gbit network. I would choose more thin client servers.

The hardware specifications listed here are based on my own experience; your mileage may vary.