Preface

We ended the first part of this article by talking about jumbo frames, having discussed some CPU considerations and general best practices for various situations.

In the meantime, the lab got the opportunity to sit down with VMware’s Scott Drummonds, who was able to provide us with some more interesting information on this subject, and a couple of our readers pointed out some of the problems they’ve been experiencing, along with the solutions. We are really happy with the overwhelmingly positive reactions we have received to Part 1, and hope Part 2 will continue to help out the people who need to work with ESX on a regular basis to get the most out of the product.

Before we dive into the more “structured” part of the article, we would like to mention a possible issue brought up by one of our readers, yknott. Apparently, IRQ sharing on certain platforms can cause a rather large performance hit in cases where the the interrupt line is used alternatively by ESX’s service console and the VMkernel. The service console is the actual console that can be logged into when an administrator wants to check out for example esxtop, and can as such take control of certain devices to perform its tasks. The problem seems to occur when both the VMkernel and the service console have control over the same device, which is something that can be checked for when displaying the /proc/vmware/interrupts file, as documented in this article of the VMware knowledge base.