Section 1.1. Introduction

1.1. Introduction

VMware produces some of the coolest software availableat least that's what I thinkand that's why I wanted to write a book about it. Virtualization has changed the way all of us think about servers and services, backup and restores, development and testing, and particularly operating systems and applications. Many in the industry believe that virtualization will change the way most, if not all, IT shops operate and that in a few years a virtualized platform will be the platform upon which most new x86-based operating systems are deployed.

Before we get started with VMware's ESX Server, let's first review the history of VMware, the company. VMware was founded in 1998. It quickly delivered VMware Workstation in 1999. A few years later, in 2001, VMware delivered GSX Server and ESX Server, both of which brought VMware into the server world. In 2003, VMware began offering Virtual Center, which included VMotion. VMotion is an incredible awesome technology that allows you to move running virtual machines from one physical ESX Server to another without powering down the virtual server. We will discuss VMotion and Virtual Center in greater detail in Chapter 8.

VMware claims nearly 3 million registered users, and at the company's VMWorld user conference, VMware stated that 5 percent of x86-based servers now run on a VMware platform.

Like many, I first started using VMware as a test platform, running virtual machines to test patches, configuration changes, service packs, and so on, but then I attended the Microsoft 2003 TechED in Dallas where many of the hands-on labs Microsoft had set up were running on VMware. Some of these labs had two domain controllers and Exchange 2003 running on a small desktop (it's funny how Microsoft now doesn't support VMwarewe'll get into that later in the book in the "Gotchas" chapter). Anyway, that got me thinking of the production network that I managed and soon I started architecting and piloting GSX and ESX server in our test environment and production environment with fantastic success. It wasn't long before we decided to cut the number of physical servers nearly in half. That made some management heads turnIT was actually going to be saving money.

So what is ESX Server? Like all VMware's platform products, Workstation, GSX, and ESX, ESX Server allows you to run multiple virtualized servers or virtualized machines on one physical computer called a host. ESX Server is VMware's enterprise virtualization product. Like its brethren, GSX and Workstation, ESX allows you to run operating systems and applications utilizing idealized hardware in a virtualized environment. Each operating system runs independently of the other, so if one operating system crashes, the other virtualized operating systems are not affected. Unlike GSX and Workstation, both of which are loaded and run on a physical computer with a preinstalled host operating system (either Windows or Linux), ESX has no preinstalled operating system and is loaded directly on the physical hardware running a highly specialized Linux kernel, the vmkernel. VMware describes ESX as its own operating system, and Chapter 9 discusses in greater length the vmkernel. ESX is much more customizable than GSX or Workstation and supports advanced configurations such as physical-to-virtual clustering, throttling of CPU, network bandwidth, and much more.

For systems administrators, VMware and ESX Server represent a truly revolutionary jump in the way you think about servers and services. VMware turns your server into a file. It's hard to comprehend that your server is a fileit was for me anyway. But as a file, you can move servers around as simply as moving files around, cutting and pasting, using scp, FTP, or whatever tool you wish. I often burn zipped-up virtual servers to DVDs and have a library of different builds (we'll discuss this issue in depth in Chapter 8 titled "Cool Tools for a Virtual Infrastructure").

Again, what VMware allows is for multiple operating systems such as Windows and Linux to run simultaneously on the same physical computer. So instead of one operating system per computer, you can run multiple and differing operating systems simultaneously, completely independent of one another. These operating systems then run the various applications and services. Why is this important? Well, for years now it has been common practice in medium- to large-sized companies to have one or maybe two applications or services running on one physical server. This, of course, has led to an enormous proliferation of servers throughout many data centers and IT departments. A majority of Callisma's customer engagements involve costsavings initiatives such as server, application, or e-mail consolidation. This proliferation, or server sprawl, adds increased IT costs in many areas. An obvious cost is the physical hardware itself. Another associated cost is administrative, which has also skyrocketed, leaving many IT managers, executives, and administrators clamoring for ways to reduce any and all costs associated with IT. VMware provides many ways in which costs can be driven down dramatically, and this will be discussed at greater length in the following chapters.

Thinking virtually can be difficult for some. When speaking with IT departments around the country, many still think physically when talking about server virtualization. There are terms and concepts that you must fully understand as you begin your virtual evolution. But once you grasp virtualization and understand its flexibility and power, you'll want to virtualize everything, at least I did. As of this writing, there are some constraints, such as a virtual server that can have no more than 3.6 gigabytes of RAM, and the fact that ESX can only support virtual Symmetric Multi-Processing (v-SMP) for two virtual processors (and by the second half of 2005, four-way virtual smp). But to me, the freedoms of a virtual world out- weigh any of its constraints. There may be times when a server cannot, or should not, be virtualized. I reiterate, there may be times, but with VMware's growing support for different operating systems and 64-bit processor architecture, servers that can be virtualized will grow in greater numbers than those servers that cannot.