The Oxide and Friends podcast had an episode on virtualizing time, specifically for the purpose of live-migrating a container from rack to rack without the VM being aware, and allowing operators to take the rack offline on their schedule. Otherwise, apparently, you end up having to leave racks running because you cannot evacuate all of the containers currently running on it. (e.g. perhaps your contracts or SLAs are such that you cannot afford even the few seconds of downtime a shut-down-here-and-spin-up-elsewhere would cause)

I believe the episode name was "Virtualizing Time"

https://pca.st/episode/c10ce39c-1348-407f-b9c2-a36ced4e6be8