Book Image

Troubleshooting vSphere Storage

By : Mike Preston
Book Image

Troubleshooting vSphere Storage

By: Mike Preston

Overview of this book

Virtualization has created a new role within IT departments everywhere; the vSphere administrator. vSphere administrators have long been managing more than just the hypervisor, they have quickly had to adapt to become a ‘jack of all trades' in organizations. More and more tier 1 workloads are being virtualized, making the infrastructure underneath them all that more important. Due to this, along with the holistic nature of vSphere, administrators are forced to have the know-how on what to do when problems occur.This practical, easy-to-understand guide will give the vSphere administrator the knowledge and skill set they need in order to identify, troubleshoot, and solve issues that relate to storage visibility, storage performance, and storage capacity in a vSphere environment.This book will first give you the fundamental background knowledge of storage and virtualization. From there, you will explore the tools and techniques that you can use to troubleshoot common storage issues in today's data centers. You will learn the steps to take when storage seems slow, or there is limited availability of storage. The book will go over the most common storage transport such as Fibre Channel, iSCSI, and NFS, and explain what to do when you can't see your storage, where to look when your storage is experiencing performance issues, and how to react when you reach capacity. You will also learn about the tools that ESXi contains to help you with this, and how to identify key issues within the many vSphere logfiles.
Table of Contents (16 chapters)
Troubleshooting vSphere Storage
Credits
About the Author
Acknowledgment
About the Reviewers
www.PacktPub.com
Preface
Index

My storage/virtual machine is slow


The following are some questions and tasks you can take to troubleshoot slow or poor storage performance.

Inspect latency values to further pinpoint where performance degradation is occurring

Tip

You can refer Chapter 4, Troubleshooting Storage Contention, for more information on this topic.

Using esxtop and thresholds in Appendix B, Statistics of esxtop, inspect latency statistics (DAVG, KAVG, QAVG, and GAVG).

  • High DAVG indicates a performance issue on the storage array or somewhere along the path to it.

  • High KAVG indicates a performance issue within the VMkernel. Possible causes could include queuing, drivers, and so on.

  • High QAVG indicates a performance issue is causing queue latency to go up. This could be an indicator of underperforming storage if higher DAVG numbers are experienced as well.

  • High GAVG is normally the total of the three previous counters. If experiencing high GAVG while other latency metrics seem sufficient, the issue could reside within the VM drivers or virtual hardware.

Ensure that your storage array is handling the demand

Tip

You can refer Chapter 4, Troubleshooting Storage Contention, and Chapter 5, Troubleshooting Storage Capacity and Overcommitment, for more information on this topic.

The following items need to be considered when dealing with storage arrays:

  • Using the formulas from Chapter 4, Troubleshooting Storage Contention, calculate on a per-LUN basis your functional IOPs requirements

  • Using esxtop and thresholds in Appendix B, Statistics of esxtop, inspect both ABORT and QUEUE statistics

    • Queuing and frequent command aborts could be a possible indicator of underperforming storage

  • Check to see if the VM has a storage profile attached to it that may have gone out of compliance

  • If possible, migrate your workload to a faster performing disk set or to a LUN with a different RAID type

  • Using esxtop and thresholds in Appendix B, Statistics of esxtop, check to see if the issue is being caused by SCSI reservation conflicts or queue depth

    • For SCSI reservation conflicts, monitor CONS/s

    • For queue depth issues, monitor QUED

  • If possible, enable Storage DRS to automatically balance your workloads