I have looked at:
- How does /will Unity handle multiple monitors? -> only two monitors with twinview
- How do I get three monitors working? -> each monitor uses a seperate x screen + xinerama (no 3d acceleration -> no Unity)
My current setup looks like this:
Two monitors in Twinview + one monitor as a seperate X screen (it is not a problem that I cannot move windows from that monitor to the other two, I used to work like this on Ubuntu 10.10). The problem with this is, that I am unable to start applications on the seperate X screen and when I manage to open a terminal on there, I am unable to interact with it (no window decoration).
I can still use my setup with the Gnome session (Ubuntu Classic), so I am not urgently looking for an answer, but I would like to know if it can be done and hopefully learn something in the process.
Edit: I should probably mention that I have two nvidia graphics cards in my computer. And that I am happy with the solution that I am currently using with gnome (i. e. TwinView + seperate X screen). This won't work with Unity as I don't know of a way to launch applications on the seperate X screen.