LTSP | LTSP Server Sizing
15 Feb 2010
RAM
LTSP website recommends 256mb for the core system plus 50mb per user:
Total RAM = 256mb + (25 users x 50mb)
= 1506mb
However Edubuntu recommends a different formula:
Total RAM = 150mb x 25 users
= 3750mb
We recommend you choose the greater of the two, and double-it if you can (see update below).
Post install update
This memory has proved a little low, mainly because we are also virtualising Windows on the same server. If you don’t require Windows, or you are providing that service from a different server, then the higher of these two figures should be sufficient; I would certainly recommend the higher figure, because of the high memory demands of Firefox and Adobe Flash.
CPU
LTSP website states that each user is likely to require around 3% of a CPU:
Total CPU = 3% x 25
= 0.75
= 75% of a CPU
So a single processor should be sufficient; however this requirement doubles or even trebles if we opt to virtualise a Windows server on the installation. We would say that a minimum of a quad-core would be sensible if virtualising Windows on the LTSP server. If this is a problem for you, simply host the Windows server elsewhere; which is probably better anyway.
Post install update
We have now upgraded both servers to dual quad-core, which is proving ample capacity. I believe a single quad-core would have been ample had we not been virtualising windows on the same server.
Network
LTSP recommend a Gigabit connection for the server and fast Ethernet for the terminals. Many fast ethernet switches include a gigabit connection, alternatively gigabit switches are becoming quite affordable.
There can be issues running LTSP via multiple switches - so if you’re buying a new switch - consider the greatest number of ports that you are likely to require.
Post install update
This has all provided to be correct - Gigabit on the server is nearly essential if you want decent performance and similarly, PCs with only old 10-base-t internet are noticeably slower to boot.