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With over 500 pages of technical content, VMware vSphere 6.5 Host Resources Deep Dive isn't for vSphere beginners. It's clear that, when they sat down to write this book, authors Frank Denneman and Niels Hagoort had administrators already well-acquainted with the ESXi hypervisor and x86 server hardware in mind. As its name implies, this book offers a deep dive into the hardware and software details that determine the maximum performance you can get out of your VMs, including instructions for how to design a virtualization platform to the specifications of the applications it delivers.
VMware vSphere 6.5 Host Resources Deep Dive is divided into four sections: CPU, Memory, Storage and Networking. These four "food groups," if you will, supply VMs with the necessary resources to function. Each section details the vSphere software that makes a particular resource available to VMs, the physical hardware that delivers that resource and the configuration of the VMs to which the resource is delivered. Denneman and Hagoort place a strong emphasis on familiarity with both the hardware and software sides of vSphere and the nature of the application that runs inside each VM.
Dive deep into CPU
Denneman and Hagoort spend about a third of VMware vSphere 6.5 Host Resources Deep Dive's 500-plus pages on CPU resources. This includes a deep discussion on non-uniform memory access (NUMA) within modern servers and its impact on VM performance, Intel's CPU architecture and bandwidth between CPUs and RAM in a server.
They then show how this physical design has driven hypervisor design to manage VMs differently, depending on the relative physical and VM CPU configurations. There are a variety of ways to optimize this behavior, depending on the nature of the application inside each VM. Considering that the authors repeatedly mention that different applications need different settings, I would have liked to see more discussion of specific applications inside VMs. The text also lacks prescriptive guidance for specific applications or guidance on how to analyze applications for their requirements.
Denneman and Hagoort show many examples of VM and ESXi host configuration in command-line tools rather than the GUI, which I find to be a good indication of their target audience. Technical staff members who are new to VMware tend to be comfortable with GUI tools, like vSphere Web Client. Many recognize the limitations of GUI after a few years of working with VMware technologies and turn to command-line tools instead.
Dive deep into memory
The second section about memory sources dives into memory channels, dual in-line memory modules (DIMM), ranks and banks, latency and bandwidth. It then moves onto the internals of the ESXi server and how its VMkernel delivers memory to VMs and arbitrates access to memory in the event of a shortage. The previous section on CPU introduces memory as it pertains to NUMA and individual CPU access to memory; this chapter builds on that knowledge and adds perspective on DIMM configuration in NUMA systems.
Denneman and Hagoort also look at the resource control settings -- Shares, Reservations and Limits -- that an administrator can apply to VMs to guide the VMkernel. I was impressed to see that the book looks at why and how the VMkernel reclaims physical memory from VMs. Although few vSphere platforms are set up to expect memory reclaim, it's a critical part of securing VM performance during a RAM shortage.
Simple and clear diagrams have been a hallmark of Denneman's previous work, and this book is no exception. This book uses diagrams to great effect to illustrate the relationship between physical and virtual resources far more clearly than words could.
Dive deep into storage
As the second-largest entry in the book, the Storage section dedicates quite a bit of time to VMware vSAN, vSphere's built-in software-defined storage. This includes a close look at local storage, particularly flash storage, as well as solid-state storage -- flash point or 3D XPoint -- the physical form factor and the type of connection from Serial Advance Technology Attachment to non-volatile memory express between the server and storage media. This focus on vSAN reflects the rapid growth in vSAN adoption. In fact, Denneman and Hagoort's coverage of vSAN is so thorough that this book is worth buying for its vSAN guidance alone.
That said, I was a little disappointed that the book doesn't provide more coverage on other storage technologies. The majority of vSphere deployments don't use vSAN, so it would have been helpful to see more information about Fibre Channel, iSCSI and Network File System.
Dive deep into networking
The final section is about networking and starts with the physical network and works up through the hypervisor into VM networking. The Networking section details many of the advanced features of physical network adapters and the benefits they provide, as well as VMkernel networking and how to optimize its network stack. Another chapter in this section looks at the various options for VM networking, including a good discussion of vMotion performance, particularly as it relates to evacuating all of the VMs of a large ESXi server to enable maintenance.
VMware vSphere 6.5 Host Resources Deep Dive lives up to its title. It also delivers a vast amount of detailed technical information about the physical hardware and the ESXi software in a vSphere environment. This information isn't essential for every vSphere administrator, but for specialists who work in mission-critical environments, this book explains many of the parts that require attention. In my opinion, this book is invaluable to architects who design vSphere environments, especially for critical applications. I expect that many readers will need to reread sections to get a full understanding, since Denneman and Hagoort pack in a lot of information.
Both Denneman and Hagoort have the credentials to support their expertise. Denneman has been a fixture of the VMware community for many years as a well-known blogger, technical consultant and, most recently, senior staff architect at VMware. Denneman's previous publications include VMware vSphere 5 Clustering Technical Deepdive, which he co-authored with Duncan Epping, chief technologist of storage and availability at VMware. As a regular reader of Denneman's blog, I can personally attest to the quality of his writing. Though I'm less familiar with his work, Hagoort is a virtualization consultant and architect with over 15 years of industry experience who specializes in enterprise cloud infrastructure and storage and networking products. Hagoort frequently covers VMware technologies on his personal blog and speaks at industry events, including VMworld and VMware User Group. Both Denneman and Hagoort are VMware Certified Design Experts, which speaks to their experience designing and operating vSphere at enterprise scale.
Though both authors are Dutch and speak English as a second language, I found the book well-written and as clear as the deeply technical content allows.
For those interested in learning more about vSphere beyond the contents of this book, I recommend the latest edition of Mastering vSphere by Scott Lowe. This series has been around for some time and is updated for most vSphere releases. I also recommend Denneman's deep dive into vSphere clustering and the IT Architect series.
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