Troubleshooting File Transfer Performance Between VM’s – Part 2

So, here we are again to finish this chapter.

After getting the Customer on a Webex session we managed to go to the BIOS settings of the DELL Server and change the System Profile to “Performance”.

BIOS Settings

So, we started the ESXi servers and we did some testings.

As a reference, before this change, the average speed to copy a 9 GB file from one VM to other was around 20 Mb/s with some drops during the transfer.

So, here are the results after:

File transfer speed after Power Management change

File Transfer Speed After Power Management Change: 55 Mbs


Power Management really matters !


Troubleshooting File Transfer Performance Between VM’s – Part 1

So, this will be my first very post.

I’ve been asked to find why the file transfer performance between 2 Windows VM’s was so poor.

So far I have to draw a strategy to start rulling out some components.

The very first thing to check at a Global level is the Power Management of the ESXi hosts.

ESXi Host offer 4 ways to control power:

High Performance: This power policy maximizes performance, using no power management features. It keeps
CPUs in the highest P-state at all times. It uses only the top two C-states (running and halted), not any of the
deep states (for example, C3 and C6 on the latest Intel processors). High performance is the default power
policy for ESX/ESXi 4.0 and 4.1.
• Balanced: This power policy is designed to reduce host power consumption while having little or no impact on
performance. The balanced policy uses an algorithm that exploits the processor’s P-states. Balanced is the
default power policy for ESXi 5.
• Low Power: This power policy is designed to more aggressively reduce host power consumption, through the
use of deep C-states, at the risk of reduced performance.
• Custom: This power policy starts out the same as balanced, but it allows individual parameters to be modified.
If the host hardware does not allow the operating system to manage power, only the Not Supported policy is
available. (On some systems, only the High Performance policy is available.

Checking the HPM (Host Power Management) MUST always be the very first thing to verify before going deeper in the analaysis.

As a reference, in the past, I had to troubleshoot a P2V of a VM that was hosting a Java application. Before Virtualization the Tomcat service took around 1 min and 30 secs to start. After Virtualization, it took 3 min and 20 secs. I have verified everything, even tried to change the Java Heap size parameters within the application and at the end I figured out, that the ESX was running on Balanced HPM. After having changed in the BIOS the HPM from Balanced to High Performance, the service toook 1 min and 15 secs to start ! Even faster than when the Server was physical !

So lesson learned: Start checking Host Power Management for any performance issue first !

For more information about this topic check this VMware White Paper

Host Power Management in VMware vSphere® 5