Virtual Machine’s CPUs Constrained due to HP Power Savings

One of the most common practices in today’s IT world, is virtualization. In the enterprise business, one of the key players is VMware with its Vsphere solution, unfortunately not all people take enough time to read best practices while installing and implementing IT Infrastructure ready for virtualization.

According to my experience one of the most difficult challenges you face as Vmware or OS Systems Administrator its performance issues. This time I’ll describe the last scenario which was causing performance issues at VM level.


Hardware: HP BL685c G7
Enclosure: c7000 G2 with 5 Blades

VMware Vsphere 5.1
VM: Windows 2008 R2 (64 bits) configured with 8 vCPus, 50G of RAM, and no limits on RAM or CPU.
Application: Oracle Database


1. Your best friend while trying to find out performance root causes, its esxtop. After launching esxtop, you may see something like this:


As you can see the %USED and %RUN differ a lot. Meaning the virtual machine want more CPU resources (%RUN) than it is actually getting (%USED). More info on this link.

2. In this case it’s evident the CPUs are being constrained, a quick look at the Server settings pointed to the root cause:


In the case of HP Servers, you must be aware of the power settings. Changing to the High Performance will avoid you headaches in the future. Take this in consideration if you are planning new Server deployments.

More References:


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