LPAR and VIO on IBM AIX UNIX Servers

Virtual I/O (VIO) and Virtualization

Briefly What is Virtualization?

The Virtual I/O Server is part of the IBM System p5 Advanced Power Virtualization hardware feature. Virtual I/O Server allows sharing of physical resources between LPARs including virtual SCSI and virtual networking. This allows more efficient utilization of physical resources through sharing between LPARs and facilitates server consolidation.

This allows a single machine to run multiple operating system (OS) images at the same time but each is isolated from the others. POWER4 based machines started this in 2001 by allowing many Logical Partitions (LPAR) to run on the same machine using but each using different CPUs, different memory sections and different PCI adapter slots. Next came with POWER4, the ability to dynamically change the CPU, memory and PCI adapters slots with the OS running. With the introduction of POWER5 in 2005, further Virtualization items have been added:

1. Less than a whole CPU can be allocated to a LPAR
2. The LPARs sharing CPUs can be setup to allow automatic load balancing (in milliseconds)
3. The sharing of disks, networks, optical devices (CD/DVD) using a VIO Server (see below)

For whole article read:
http://www.ibm.com/developerworks/wikis/display/virtualization/VIO
Source: IBM DeveloperWorks Wiki