With Proxmox, several physical servers are joined into a cluster. The virtual servers are spread across the cluster and can be moved between the computers, for example when one of them needs to be updated.
Activator.se runs on a Proxmox cluster in our own environment. On top of the cluster the solutions run in containers, with our own container registry and a cap on the number of requests in front. That gives us control over where data is, without a licence fee for the platform itself.