Using Xen (https://xenproject.org/ https://xenproject.org/), you can live migrate running Virtual Machine containers from one physical computer to another on co

Using Xen (https://xenproject.org/ https://xenproject.org/), you can live migrate running Virtual Machine containers from one physical computer to another on commodity PC hardware while continuing to serve requests (no down time). You can then turn off the computer the VM was originally running on, upgrade it then migrate the VM back to it again. I did this once while pinging the VM from another machine. It didn't even drop any packets. My jaw dropped though.