Book Image

vSphere High Performance Cookbook

Book Image

vSphere High Performance Cookbook

Overview of this book

VMware vSphere is the key virtualization technology in today's market. vSphere is a complex tool and incorrect design and deployment can create performance-related problems. vSphere High Performance Cookbook is focused on solving those problems as well as providing best practices and performance-enhancing techniques. vSphere High Performance Cookbook offers a comprehensive understanding of the different components of vSphere and the interaction of these components with the physical layer which includes the CPU, memory, network, and storage. If you want to improve or troubleshoot vSphere performance then this book is for you! vSphere High Performance Cookbook will teach you how to tune and grow a VMware vSphere 5 infrastructure. This book focuses on tuning, optimizing, and scaling the infrastructure using the vSphere Client graphical user interface. This book will enable the reader with the knowledge, skills, and abilities to build and run a high-performing VMware vSphere virtual infrastructure. You will learn how to configure and manage ESXi CPU, memory, networking, and storage for sophisticated, enterprise-scale environments. You will also learn how to manage changes to the vSphere environment and optimize the performance of all vSphere components. This book also focuses on high value and often overlooked performance-related topics such as NUMA Aware CPU Scheduler, VMM Scheduler, Core Sharing, the Virtual Memory Reclamation technique, Checksum offloading, VM DirectPath I/O, queuing on storage array, command queuing, vCenter Server design, and virtual machine and application tuning. By the end of this book you will be able to identify, diagnose, and troubleshoot operational faults and critical performance issues in vSphere.
Table of Contents (15 chapters)
vSphere High Performance Cookbook
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Setting the right time in Guest OS


Time measurements within a virtual machine can sometimes be inaccurate due to difficulties with the guest operating system keeping the exact time.

Because virtual machines work by time-sharing host physical hardware, virtual machines cannot exactly duplicate the timing activity of physical machines. Virtual machines use several techniques to minimize and conceal differences in timing performance. However, the differences can still sometimes cause timekeeping inaccuracies and other problems in software running in a virtual machine.

Several things can be done to reduce the problem of timing inaccuracies:

  • You should always try to use guest operating systems that require fewer timer interrupts

  • Different operating systems and versions have different timer interrupts. For example:

    • Windows systems typically use a base timer interrupt rate of 64 Hz or 100 Hz, which means 100 interrupts per second

    • 2.6 Linux kernels have used a variety of timer interrupt rates (100 Hz...