Has anyone tried setting this up on a DS918+ and want to share the experience? I'm a Docker newbie so a little guide for this setup (I assume there would be two Docker-containers in this case?) would be great.
VMM uses the QEMU/KVM Stack under the hood, which has build in support in the hosts kernel. I am not using VMM, but I have experience with QEMU/KVM. Openstack uses it as it's virtualization layer. Seems to be good enough of a choice that people use it to create their private clouds... It can't be that terrible
Virtualized GUIs are always slow, unless the vm provider is able to use para virtualization to delegate at least parts of ui rendering to an actual gpu.
And then there is also this partbreaker. you won't be able to run VBox in a container, unless you don't load the required kernel extension /dev/vboxdrv on your Diskstation and pass it into the container. Oddly you will need a VBox installation on your Diskstation in order to be able to run one in a Docker container.