REVIEW: Essential Virtual SAN (VSAN) 2nd Edition


On Friday my pre-order of Duncan Epping’s and Cormac Hogan’s updated book for VSAN was finally available for download. A few clicks on the website of PearsonITcertification and I was ready to start reading. I took the whole weekend to read this book.


The structure of the book:

The books reads very pleasantly mostly because it has been well structured, and despite the technical nature of the content of this book (of course this is why we buy it), it is easy to follow. ‘Essential Virtual SAN (VSAN) 2nd Edition’ contains ten chapters:

  1. Introduction to VSAN
  2. VSAN Prerequisites and Requirements for Deployment
  3. VSAN Installation and Configuration
  4. VM Storage Policies on VSAN
  5. Architectural Details
  6. VM Storage Policies and Virtual Machine Provisioning
  7. Management and Maintenance
  8. Stretched Cluster
  9. Designing a VSAN Cluster
  10. Troubleshooting, Monitoring and Performance

It should come as no surprise that understanding the differences between the releases and getting to know the new features and improvements which come with VSAN6.2 is rather important. Even though this book for the most part deals with VSAN 6.2, it does contain the necessary comparisons with VSAN5.5, VSAN6.0 and VSAN6.1. For example where VSAN5.5 and VSAN6.0 only leverage RAID-0 and RAID-1, VSAN6.2 can leverage RAID-5 and RAID-6 as well. How this impacts your design and ultimately the performance and ‘dimensions’ of your deployment is well explained in this book.

Here are some of the highlights for me:

Despite the fact that VSAN is relatively easy to setup and can be achieved in under 1 hour, there are  prerequisites and requirements which you should not ignore. The authors present the readers with a comprehensible list and installation steps and procedures in chapter 2 and 3.

If you ever wondered what makes VSAN tick under the hood, Duncan and Cormac touch this subject very briefly in chapter 5. The software components which make up VSAN are explained here from a high level perspective. Chapter 5 of course contains more than just an overview of the software components, it also explains the 5 different types of objects on a VSAN datastore (The VM home or “namespace directory”,  A swap object (if the VM is powered on),  Virtual disks/VMDKs,  Delta disks (each an object) created for snapshots,  Snapshot memory (each an object) optionally created for snapshots); the On-Disk formats, cache devices, VSAN i/o flow, the role and function of the cache layer; data locality in a normal VSAN cluster and in a stretched VSAN cluster, witnesses and replica’s and so on.

Chapter 6 deals with VM storage policies and VM provisioning is one of the most important chapters to me. Personally I think this is one of the harder subjects to get a grip on when you have no hands-on experience and when you are dealing solely with whitepapers and blog posts. This chapter is a true gem when it comes to explaining the storage policies and VM policies. This chapter contains some very good examples using different scenarios on how policy settings might impact your environment. If you want to know exactly how FTT, stripes, RAID-0, RAID-1, RAID-5,  RAID-6 and other parts make up the storage policies, this is the chapter for you to read. By the way, did you know there are scenarios where you have more than 1 witness and sometimes don’t even need one? (That last bit is not entirely true as you will find out in the book). A little tip: go to and open HOL-SDC-1608 What’s New with Virtual SAN 6.2. It might be nice to check all these steps mentioned in the book also in the free online lab provided by VMware.

Never assume that a VSAN cluster reacts identical to a normal ESXi cluster in vCenter server: Did you know that VSAN actually doesn’t need vCenter server to keep running and provision VM’s? You can actually do that with scripting as well. Maintenance mode, replacing disks and removing hosts require a different set of procedures as well. Definitely read chapter 7!

Chapter 9 delves into the specifics of building a VSAN Cluster. The authors describe in this chapter how you can design a VSAN cluster and which tools you can use. Anyone who considers setting up a VSAN cluster into production should not skip this chapter. If you consider setting up a Stretched VSAN Cluster, don’t skip chapter 8 either. Personally I would have placed chapter 9 before chapter 8 in the book but that is just me of course.

Throughout all chapters of this book you will find tips, not just the normal tips like changing a setting left and right, but also valuable lessons VMware has learned while taking care of deployments for customers. For example Cormac and Duncan are not too shy to share how many VSAN nodes most customers use per cluster and why. PS, this number does not match the Configuration Maximums specified in the official documentation. Speaking about tips, Chapter 10 contains more than 70 pages of Troubleshooting, Monitoring and Performance tips!

Why this book stands out from the crowd:

The most obvious reasons of course are that Essential Virtual SAN has been written by Duncan and Cormac, two very respected persons in the industry and that it deals with VSAN 6.2, the most recent version of VSAN. I did get a bit of a pleasant surprise too though because this book really tries to provide solutions and is not just the next technical marketing book. The writers really try to keep it real by mentioning best practices learned in the field while helping customers, tips tricks and troubleshooting methodologies. This book is so much more than just a book about configuration settings. If like me you like cars, this book is like a owner’s manual for car owners, but than for VSAN owners, designers and architects.


If you like to know more about VSAN and are considering testing and deploying VSAN 6.2, this book is a ‘must read’. While the first edition dealt with VSAN 5.x, this updated version deals with VSAN 6.2.  To be honest this book contains more than enough new bits and pieces to justify buying the new edition of Essential Virtual SAN. I really think this book is a blast!

I am sure everyone who has a keen interest in Hyper Converged Infrastructure, VSAN, or is chasing VCAP certification will enjoy this book and will find it contains a wealth of information.

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