Ubuntu: How to set each workspace to a separate monitor

The original author was asking about different workspaces on each screen, not a single workspace stretched across both screens. I'm trying to configure the same. Does anyone have any pointers on how to do this?

Doing so, you could pull up either workspace on either screen and also still drag / move windows between workspaces. I think this is a much better solution if you are using a laptop display and an external monitor - if it is possible.

perhaps this is what you're looking for: http://ubuntuforums.org/showthread.php?t=826717

Basically, from that thread, I'd edit /etc/X11/xorg.conf, and modify the "Screen" section (add red text):

Section "Screen"
    Identifier "Default Screen"
    Monitor "lcddisp"
    Device "Configured Video Device"
    DefaultDepth 24

    SubSection "Display"
        Virtual 3120 1050
    EndSubSection
EndSection

3120 is the sum of both monitor's resolution width (1680 + 1280), 1050 is the max of the resolution's height (1050 > 800).

Restart X (Ctrl-Alt-Backspace), then go to System > Preferences > Screen Resolutions. From there, you can turn on/off one of your monitor, or turn on both cloned, or turn on both side by side (as in dragging windows from one to another).

The only downside to me is that my Intel 965 has a 3D buffer size of 2048x2048 so 3D Compiz looks weird if I have two monitors in side-by-side mode (3120px is way too big to fit on 2048px buffer).

Read that post for more detail.

Source :http://ubuntuforums.org/archive/index.php/t-888979.html