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Get It Right: Power Management in vSphere

I was recently deploying a virtual appliance, and found that a very specific BIOS setting on CPU power management was causing consistency issues in my vSphere cluster. Specifically, if I used one host for this virtual appliance, it worked fine. But the moment the vSphere Distributed Resource Scheduler (DRS) would assign the virtual appliance to another host, it wouldn't power on. This virtual appliance was requiring specific CPU settings in the host BIOS. After the issue was resolved, I decided to investigate further.

What I found is that I had a cluster that was, generally, set up well and consistently. Consistent configuration of your hosts is the key to a vSphere cluster performing well. The one area where I had an anomaly was the CPU power management policy in the host BIOS, which is a very specific setting. It reminds me a lot of the "virtualization-enabled" situation that I had a few years ago, but this one was much more specific. The host CPU BIOS is displayed as a power management value in the vSphere Web Client, as shown in Figure 1.

[Click on image for larger view.] Figure 1. The host has specific information on the CPU visible as a policy object.

The "Not supported" value in this example is where the host CPU power management policy can't be applied. This feature is documented on the VMware site as you'd expect, but this is an interesting area to consider. Regardless of how I arrived at this problem, I think it's worth taking a look at each host in a vSphere cluster to see if this value is consistent for each host.

Personally, I feel that performance is more important than power management for today's modern processors. Hosts that I manage with modern processors have different options, such as balanced or high performance and so on. You can change part of the option in the vSphere Web Client, but it depends on what options are set in the BIOS.

Has CPU power management ever interfered with a virtualization configuration you've used? Further, are your hosts configured consistently in this regard? Share your experience about CPU power management below.

Posted by Rick Vanover on 01/30/2015 at 10:26 AM


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