The Effects of HP’s Power Profile on vCPU Performance

When you buy a new HP server it comes with the BIOS setting HP Power Profile set to Balanced Power and Performance. That sounds good but is bad – at least for CPU performance in a VDI environment.

When we prepared our servers for use as virtualization hosts for Citrix XenDesktop we took great care to configure the HP Power Profile for Maximum Performance:

BIOS setting - HP power profile

That fixed the problems with really awful CPU performance we had in the beginning. But still – some VMs were performing worse than others. When I looked at the problem I soon found a VM with bad CPU performance. I ran some benchmarks, comparing it to a “good” VM:

Test setup:
CPU: Xeon E5-2670 2.6 GHz
Hypervisor: VMware ESXi 5.0 Update 1
VM OS: Windows 7 64 Bit
VM configuration: 2 vCPUs

Benchmark Good VM Bad VM
Cinebench 11.5 CPU
>> more is better
2.20 1.48
NovaBench CPU Test
>> more is better
262 204
Super Pi 1M [s]
<< less is better
13.2 32.2

Depending on the benchmark, the “good” VM is between 28% and 244% faster than the “bad” VM. That is a lot!

I suspected the power profile setting of the server hosting the “bad” VM to be wrong, but how to check without rebooting the server and accessing the BIOS? These are production systems and we cannot use vMotion to move the VMs off the server because the VMs are on local storage. Luckily the power profile setting is not only available from the BIOS, but from the iLO console, too. It can even be changed from iLO, taking effect immediately:

iLO Power Settings

Sure enough, the “bad” VM was on a server with incorrectly configured power profile. Switching it to HP Static High Performance Mode fixed the issue. Strangely, the settings are named differently in BIOS and iLO.

If you want to know more about power profiles and power regulator: HP has a whitepaper on the topic.

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3 Responses to The Effects of HP’s Power Profile on vCPU Performance

  1. Gabrie van Zanten July 18, 2013 at 09:16 #

    Hi
    Can you tell me how you tested? My guess (but I’m not sure either) would be that if you have no load on the host and then suddenly run these tests, that the test results will show a difference compared to when you run the tests for an hour or so and fully load the host.

    Would you have more information on how HP’s performance mode works? When it “kicks in”? Think that is very important with your testing.

    Gabrie

    • Helge Klein July 18, 2013 at 11:19 #

      Hi Gabrie,
      I ran the tests on a production machine, i.e. the host had about 30 VMs running a VDI workload. As I mentioned in the article I noticed badly performing VMs in production and could not reboot or do a vMotion. So I simply logged on to the badly performing VM (Win7 x64), ran the benchmarks a few times, changed the power profile setting and ran the benchmarks again.
      Helge

  2. Barry Schiffer July 30, 2013 at 12:06 #

    Thanks Helge, already knew it needs to be changed but wasn’t expecting dramatic results. Just started troubleshooting a performance issue for a customer and this setting already helped a bit. At least performance counters are not influenced anymore by power settings.

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