3.1.2-0ubuntu2 here too, and if you ls /var/run/md* in the running system you don't have the mdadm.map file?
From the comments I am not sure if 3.1.2 is supposed to already have that unplug support or not, at least for me it does not yet unbind unplugged disks automatically. https://raid.wiki.kernel.org/index.php/Hotplug
3.1.2-0ubuntu2 here too, and if you ls /var/run/md* in the running system you don't have the mdadm.map file?
From the comments I am not sure if 3.1.2 is supposed to already have that unplug support or not, at least for me it does not yet unbind unplugged disks automatically. https:/ /raid.wiki. kernel. org/index. php/Hotplug