“The s390 is the grand-daddy of virtualization. Everything started there. In so many ways, everything we’re doing with x86 virtualization is just playing catch-up. The new exciting features like hardware virtualization support and hardware paging support have been in s390 forever.”

“s390 clearly has a very mature hypervisor. What many people may not know though is that it’s normal to run two hypervisors at any given time on s390. At the bottom level, there’s PR/SM which divides the machine into rather coarse partitions. Within a PR/SM partition, you can run z/OS or Linux. You can also run z/VM within a PR/SM partition. z/VM is another hypervisor that allows for much more sophisticated features like memory overcommit and processor overcommit. The user has the ability to decide how much hypervisor they need to maximize the efficiency of their workloads.”