Hypervisors on LinuxONE (part1)

In the last post I described high level how flexible IBM LinuxONE is in regards to resource assignment and separation. As mentioned in this post the reason for its flexibility is based on the different levels of Hypervisor IBM LinuxONE is able to run.

As you might have seen this is part 1 so there will be not only one Hypervisor I will have a closer look at.

I will start with PR/SM. PR/SM or Processor Resource/System Manager is a Layer 1 Hypervisor, maybe first explain what types of Hypervisor exists.

Hypervisors are grouped into two segments. Layer 1 and Layer 2. A Layer 2 Hypervisor uses and existing Operating system, such as Linux or Windows to manage multiple guests within a Host operating system. Where the Layer 1 Hypervisor is part of the Bios or Firmware running direct on the bare-metal Hardware.

As already mentioned, PR/SM is a Layer 1 Hypervisor and is part of the firmware, which manages the LinuxONE system. With PR/SM it is possible to partition the available hardware into multiple logical segments. Such a segment is called LPAR (Logical Partition). You can assign dedicated CPU, Memory, Storage, Network, meaning all available resources of an LPAR and establish hardware segmentation or you can let PR/SM manage the runtime assignment of the real use and share IFL and other resources between multiple LPAR. The usual usage is to share, as the term "logical partition" suggests, to increase the utilisation of the available hardware. The customer has the choice, based on their needs to choose how to use the hardware in the optimal way. If there is the need to true isolate, without any option to break or notice other workloads on the same physical box, you can establish this on LinuxONE. LinuxONE is certified at EAL5+ showing not only the ability of PR/SM and the firmware to share resources, but as well to isolate them at a really high level.

So far I have not been able to see details of the PR/SM logic, but what I know is that it takes a lot of features into its computation, where a current requested operation should be scheduled.

PR/SM enabled LinuxONE and System Z to establish its power. Been able to run applications at a regular 80% utilisation enabled customers to consolidate multiple applications or many instances of the same type on a common hardware and reduce the needed space, energy and costs of the overall system.

The next Hypervisor I will look at is zVM, I hope to have it finished as the next one, but maybe there is something different getting on my way.