PowerVM is the virtualization environment for AIX, Linux, and IBM i running on the IBM POWER hardware platform. This white paper provides an overview of PowerVM concepts, architecture, terminology, and capabilities.
Today, all major processing hardware platforms support the ability to create virtualized instances of a single server. IBM's proprietary POWER (Performance Optimized With Enhanced RISC) architecture is no exception; the complete virtualization package encompassing all necessary components is termed PowerVM.
While the basic concept of the virtual machine is generic, each specific implementation has its own architecture and associated terminology. In this paper we will present an overview of the PowerVM architecture indicating the relative place and function of each of the major components.
We will start with a big-picture look at the architecture and then introduce some of the functionality offered by this platform.
The Big Picture
The major architectural components and terms are illustrated in Figure 1. The key components are the Managed System, the Flexible Service Processor (FSP), Logical Partitions (LPARs), and the Hardware Management Console (HMC).
The Managed System
This is the major hardware component; what would perhaps more commonly be termed a server. This is the physical computer holding processors, memory and physical I/O devices. Managed systems can be broadly divided into three categories-small, midrange, and enterprise. They can also be classified based on the processor architecture. As of 2014, IBM is beginning to ship P8 systems (P8 designated POWER8, or the 8th generation of the POWER chip architecture released since its debut in 1990), however the majority of systems currently in production would be P7 and P6, and there are still more than a few P5 systems running.
Several general statements can be made about a managed system:
- All managed systems are complete servers, i.e. they have processors, memory, and I/O devices
- The number of processors varies depending on the system model. Small systems will typically have up to eight processors, midrange systems will scale up to sixty-four, and the enterprise P795 system (currently the largest) scales to 256 processors
- In any one managed system all processors will be the same architecture and speed, i.e. all 4.25 GHz P7 or all 4.2 GHz P8
- Like the number of processors, the number of memory slots also varies by model, as well as the capacity of the memory modules installed in those slots. Small servers might typically have a total of up to 64 GB memory, midrange servers up to 2 TB, and the P795 supports up to 16 TB of memory
- Midrange and enterprise class systems are designed to be scalable, hence a system can be ordered with a minimum amount of processors and memory and subsequently expanded by adding plug-in components up to the maximum capacity of the model of system; such expansion normally requires downtime to physically install the additional hardware
- In most cases systems have a fixed number of Peripheral Connect Interface (PCI) I/O device slots, the PCI version depending on the age of the server and which PCI variant was current at the time the server was introduced
- I/O capacity can be increased by adding I/O drawers containing either PCI slots, disk drive bays, or a combination of both slots and bays; these drawers are separately rack mounted from the server and connected using the Remote IO (RIO and RIO2) IBM proprietary loop bus architecture
- Most managed systems (the only exception being POWER blades, which are not very common) have a Flexible Service Processor (FSP), which is a key component in the virtualization architecture.