Ubuntu – Dual Monitors: Cannot switch workspace on VGA monitor

I have a dual monitor setup with an internal laptop monitor and an external VGA monitor (extended, not mirrored). When I now switch workspaces, this only happens on the internal monitor; windows on the external monitor are always "sticky"!

What I would want is the workspace stretching over both the internal monitor as well as the extended external monitor, and switching workspaces should have the same effect on both monitors.

I do not want to establish separated workspaces on each monitor which are switchable individually. This is a feature for which I found several questions here on the platform, but for my specific problem I was not able to find a solution or even a matching question…

My system is an Ubuntu 13.10 (currently with Gnome Shell) with kernel 3.12. The laptop has an nVidia Optimus graphics adapter; I basically always rely on the precessor's internal graphics adapter.

Thanks in advance!

/edit:

I resolved the issue now. It turned out that it is actually a Gnome problem, this is why I did not find anything with my Ubuntu related search attempts.

You find the solution here: http://gregcor.com/2011/05/07/fix-dual-monitors-in-gnome-3-aka-my-workspaces-are-broken/

The desired behavior is activated by executing

gsettings set org.gnome.shell.overrides workspaces-only-on-primary false

in a shell.

/edit (2017-10-26):

The sketched solution does not work anymore for me in Ubuntu 17.10. A working solution is given in this answer: How can I make gnome-shell treat both monitors in the same way?:

open gnome-tweak-tool and, under "Workspaces", change the "Workspaces only on primary display" setting.