To have a fixed setup of workspaces in Ubuntu unity, install the
compiz config settings manager and start it:
$ sudo apt-get install compizconfig-settings-manager
$ ccsm &
General Optionsthere is a tab
Desktop Sizethat allows to specify the number of horizontal and vertical workspaces. I usually work with a 3×2 grid.
To quickly navigate between the workspaces, use <alt><arrow keys>.