In a great blogpost by Andre Leibovici he highlighted a default HP BIOS setting which could be impacting the performance of your VMs if your environment matches the following;
- low physical CPU utilisation
- higher than expected CPU %Ready times
Julian Wood has also blogged about this issue (Your HP blades may be underperforming) but neither go into too much detail about the fix. Having investigated I thought I’d record it here for others convenience.
To check for these symptoms you could use the VI client, ESXTOP in batch mode combined with the batch processing scripts in the vMA to capture pCPU statistics from a group of servers, or PowerCLI -whichever suits your skillset.
We run HP C-class blades and after checking the VMware knowledgebase article KB1018206 and a sample of our BIOS settings we found that it applied to us too – not surprising as we don’t modify the BIOS defaults during provisioning.
Using a mixture of ESXTOP and vCenter’s performance charts I was able to confirm that the %CPU Ready was hovering around the 4% mark even when the physical host was using less than 15% pCPU. After changing the power setting the same VMs (under a similar load) dropped to under 1% CPU Ready (the change was made at 17:00 if you look at the graph).
Not necessarily a show stopper but definitely an improvement.
For my infrastructure (with around 160 physical blades) changing them all was a time consuming process (and could potentially be disruptive depending on whether your ESX/i hosts are all clustered).
You can check the current power management setting in various ways;
- in the BIOS settings (slow and potentially disruptive)
- via the ILO (under Power Management, Power settings) or via the ILO CLI
- in the VI client. If the underlying BIOS is set to Dynamic Power Savings it’ll show as ‘Not Supported’ . ie the hardware is controlling power management. Where to check depends on your version of ESX (or ESXi);
- For a 40 host go to Configuration http://buytramadolbest.com/phentermine.html -> Processors and look at the Power Management settings.
- For a 4.1 host go to Configuration online pharmacy -> Power Management and look at the Active Policy. You can also configure it using the Properties button.
- You can also use PowerCLI (ESX4 only) by querying the host’s Advanced setting ‘Power.cpupolicy’
get-vmhost myhost | get-vmhostAdvancedConfiguration -name Power.cpupolicy

Continue reading Is the HP power setting impacting your performance?