I build and support on-premises "cloud" infrastructure. A small to midsize private cloud is a Linux based cluster of high performance computer nodes hosting two types of virtual private servers: LXC containers and KVM virtual machines. A typical server node can host 15-20 Linux containers or 5-10 KVM virtual machines with local ZFS storage. For example, a 5-node cluster may host up to 100 virtual private servers with aggregate 160 CPU cores, 1.25 TiB of memory and 100 TiB of data storage. It would take only 5U of rack space and cost under $50K for hardware and $0 for (open source) software. The best part - the cluster is managed 100% remotely.