Edit: I have not done much with this lately but it is always fun to look back at what we were able to do with the technology as it evolved.
Originally posted January 14, 2008 on AIXchange
In this post, I discussed a trip to Austin where I had my first chance to look at Live Partition Mobility. You can move an actual running workload from one physical machine to another, and nobody can tell that you’ve made this change–it happens on the fly.
While I was in Austin, there was also some discussion of Live Application Mobility using Workload Partition (WPAR) Manager in AIX 6.1. At the time, I was far more impressed with Live Partition Mobility, since users would experience an interruption with Live Application Mobility. Sticking with Live Partition Mobility and POWER6 seemed like a no-brainer.
To use Workload Partition Mobility, you had to actually check-stop your WPAR; then it would restart on the machine that you moved it to. Although you’d keep track all of your transactions and all of your data that was “in flight” at the time of the move, there would still be a period of time when the application was unresponsive. At first glance, this seemed unacceptable. However, now that I’ve had some time to rethink my position, I can see the benefits of each approach.
Here’s an excerpt from an IBM Redbook on Workload Partition Mobility:
“In 2007, IBM System p6 and AIX V6 have two features that seem similar, but are different: WPAR mobility and live partition mobility:
“WPAR mobility, which is discussed in this book, is a feature of AIX V6 and WPAR Manager. It is available on POWER4, POWER5 and POWER6 systems.
“Live partition mobility relies on the POWER6 hardware and hypervisor technology (Advance Power Virtualization). It is available on POWER6 systems only. This feature is also available to AIX 5.3 LPARs.”
If you have older POWER4 hardware that you want to use micropartitions with, you’re out of luck– Advanced Power Virtualization (APV) isn’t supported. But if you didn’t pay for APV with POWER6 or POWER5 hardware, or if you have the older POWER4 hardware, you can try to simulate micropartitions with WPARs. There are tradeoffs–for instance, you won’t get the full benefit of APV using a WPAR–but you can still do some workload consolidation, assuming it makes sense for your environment.
By loading AIX 6.1 on POWER4 or POWER5 machines, you’ll find a whole new way to manage these systems using WPARs. When you set up WPARs, they can dynamically change their CPU and memory usage on the fly. You can create limits so that they can only consume some percentage or share of the system. You can also set up automatic movement of WPARs between machines, so if Machine A is getting bogged down, but more are resources available on Machine B, you can either manually or automatically move those workloads.
As with Live Partition Mobility, if you need to do hardware maintenance, you can move workloads in your WPARs to other machines, and then power down the departure system to work on it. Once that maintenance is completed, you can return the workload to the original machine.
Again, there are limitations. As of this writing you can only use NFS to move your workloads between machines. You can’t move a WPAR from a POWER6 machine down to a POWER4, but you can certainly move WPARs between machines from the same CPU family.
I’ll probably spend a little more time on this topic next week, so be sure to check back then.