Hyper-V and BIOS power plans (c-states)

“Scotty, I need more power!”

Growing up watching Science Fiction programs, one of my favorite characters was Scotty from Star Trek. He always came through in a tough situation with an answer that would get more performance or power from the Enterprise when they needed it the most.

On that note, let’s talk about some power settings on your Hyper-V hosts. Microsoft works with the hardware vendors to try to have the best default settings for servers out of the box – balancing power loads and performance. At customers sites though, we have seen instances where tweaking the power settings is needed to provide the best performance for your Hyper-V Hosts.

How long does it take for you to do a live migration between hosts?

I ask that of all the customers I talk to that are using Hyper-V. If your answer is more than 30 seconds, then you should probably look at the settings mentioned below. This timeframe also depends on the load of the host, the load of the VM, the Live Migration network, and the amount of memory the VM is using. But, if you have a VM with 4GB of RAM that is not doing anything (a completely new VM for example) the cluster is not under a heavy load, and it takes longer than 30 seconds to Live Migrate, then this blog post is for you. I have been to some customers where a Live Migration took over 3 minutes – and one of them was even closer to 10 minutes!

In the BIOS of newer servers, there are Power Plan options. We have seen different setting depending on the make and model of the server. Below are the general settings we recommend changing.

On HP servers, we have found the following settings are sometimes needed:

HP Power Plan:	Maximum Performance
HP Power Regulator:	HP Static High Performance Mode
Minimum Processor Idle Power Core State:	C6 State
Minimum Processor Idle Power Package State:	Package C3 State

On Dell servers, we have found the following settings are sometimes needed:

Power Setting:	High Performance
C1E:	Disabled
C State:	Disabled

I hope this helps your Live Migrations move at “Warp speed”!

David Hail | Premier Field Engineer – Platforms
Microsoft Services | US, Central Region, Heartland
dhail@microsoft.com