AIX Enhancements -- Workload Partitioning
The most exciting POWER6 enhancement, live partition mobility, allows one to migrate a running LPAR to another physical box and is designed to move running partitions from one POWER6 processor-based server to another without any application downtime whatsoever.
There are some exciting virtualization enhancements being introduced with the new POWER6 architecture, including live partition mobility, shared dedicated capacity and integrated virtual Ethernet. The most exciting of these enhancements, live partition mobility, allows one to migrate a running LPAR to another physical box and is designed to move running partitions from one POWER6 processor-based server to another without any application downtime whatsoever. Other exciting innovations also scheduled for 2007 availability include workload partitions (WPARs) and live application mobility.
Some get confused that these enhancements don’t stem from the POWER6 architecture or the hypervisor used to power IBM’s Advanced Power Virtualization (APV), but OS enhancements brought about by the introduction of AIX V6.1. This article will discuss these enhancements, what exactly they are and what you’ll be able to do with them.
Workload partitions (WPARs) allow for the usage of separate partitions with only one AIX image. This provides you with the flexibly of having separate environments without the burden of having separate OSs. These are different than LPARs in that you can create these environments without having to configure and administer separate AIX copies of the OS. Each WPAR has its own memory and file space separation from other partitions, but they share common AIX libraries. They’ll also have their own network and security.
Unlike the introduction of LPARs, which required the new POWER4 architecture, WPARs don’t require the POWER6 architecture and can run on POWER5 systems. They do, however, require AIX V6.1, due to be released later this year. One of the primary benefits of WPARs is that administrators won’t have to upgrade each AIX instance to a new version as one needs to do with an LPAR. This is because a group of WPARs will have only one instance of AIX, unlike LPARs. Each WPAR will obtain a regulated portion of system resources available to the single image while sharing kernel resources and I/O. Furthermore, each WPAR is a separate administrative and security domain.
In a way, WPARs are an admission on the part of IBM that its virtualization and partitioning strategy needed to grow to provide more options and greater flexibility for IT managers. Sun has provided this ability for years through Solaris containers. Over the years, IBM emphasized the superiority of the LPAR strategy over the Sun container strategy. For instance, the primary benefit of having separate partitions with separate OSs was having different versions of OSs and/or maintenance levels running on one physical box. This provided a high degree of isolation between each partition, as each partition is like its own physical server. Because each partition functions as its own logical server and provides this higher degree of isolation through their hypervisor, IBM’s LPAR-based strategy also allowed one to run Linux partitions as well, on their POWER5 architecture.
However, IBM’s marketing challenge now is to clearly show that the WPAR feature wasn’t introduced just to mimic Solaris containers’ similar capabilities, but as a complement to LPARs and their virtualization strategy. Indeed, some IBM folks have already stated that the WPAR features were part of a larger strategy started years ago with the zSeries platform, prior to the introduction of Solaris containers. Also, WPARs provide capabilities that containers don’t: higher isolation with logical partitions, live relocation of WPARs, several types of WPARs (application and system), multi-system management of WPARs, policy-based relocation and thread, and process and paging isolation (containers provide only memory and processor isolation).
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