I have an ESXi 5.5 host called ESXi1 in a host DRS group called "ESXi1 Host group". No other ESXi hosts are in that group, but there are 4 other ESXi hosts in the cluster. I have a VM called "VM1" in a Virtual machine DRS group called "VM1 virtual machine group". No other VMs are in that DRS group.
VM1 -> "VM1 machine group"
ESXi1 -> "ESXi1 host group"
There is a mandatory DRS rule that says that VMs in "VM1 machine group" can only run on ESXi hosts in the "ESXi1 host group". What happens when I try to put host ESXi1 into maintenance mode? Will it be able to evacuate VM1 since there are no other hosts in the group that VM1 has to run in?