Hyper-V has evolved since its release back in 2008. At that time, Hyper-V was released as an update to Windows Server 2008, KB950050 to be more precise (which can be found at https://support2.microsoft.com/kb/950050/en-us). Many of the features available today were not present at that point. If you take a look, you can actually see that virtualization has been one of the areas of major investments by Microsoft, not only with Hyper-V, but also to ensure that all its major products would be able to run perfectly on a virtualization environment. As an example of how Hyper-V has evolved, Microsoft Azure runs entirely on it. In the first release, Hyper-V did not have Live Migration, Storage Live Migration, Replica, Dynamic memory, and many other features. It also had support for only four virtual processors and 64 GB of virtual RAM per Virtual Machine (VM). At first, Hyper-V's only appeal was its price, or the fact that it is not charged at all.

Nowadays, Hyper-V is the leading virtualization solution in many markets and is rapidly gaining market share over its competitors. The reason behind this is actually simple. Hyper-V combines a solution that meets the higher expectations of large enterprises and since it's delivered free, even small companies can benefit from all Hyper-V features. Moreover, Microsoft Hyper-V Server is a totally free virtualization platform with no restrictions, compared to the Hyper-V from Windows Server, and is a perfect scenario for open source users too. Licensing and Utilization options will be explained in detail in Chapter 3, Licensing a Virtualization Environment with Hyper-V, so for now, all you have to keep in mind is that Microsoft delivers all its virtualization technologies at no cost.

However, before we go through all the Hyper-V features that this book will cover, it's important to understand the architecture and components of Hyper-V, so you'll have a better understanding on how all this works and will be able to make better decisions when planning your virtualization environment.

In this chapter, we will cover the following topics:

Looking back in history, Hyper-V is not the first virtualization technology from Microsoft. Actually, virtualization, emulation, and other techniques have been used since the first computer was released. Even mainframes use these techniques. Specifically, virtualization, as we know today, was imagined to solve a common problem, that is, the average utilization of a server is extremely low. Even though some components are used more than others, the total utilization of a server is minimal. That happens because when you plan for a server that will run an application, you have to plan for the higher utilization moment, when an application is stressed. But this utilization peak will occur just a few times during the month. For all other times, your server will be either idle or using 5 to 10 percent of all its capacity. That is the average. Before virtualization, another technique was also used: server consolidation. This technique consists of running multiple applications on the same server. The problem with this option is that you have no isolation between the application environment, and often, you can't combine too many different applications on the same server as they may have totally different requirements. Another problem of the server consolidation is that the utilization peak will create another problem of two concurrent applications on the same server. This technique is hardly used today, as virtualization addresses these issues in a much better way.

Microsoft has played in this field of better hardware utilization since its first operating system. Even Microsoft DOS had some options for doubling RAM. Windows 3.X introduced paging, also known as virtual memory, on later Operating Systems (OS). The game started to change in 2003, when Microsoft bought two products called Virtual PC, which already had released versions for Mac OS and Windows, and Virtual Server, which was in the development phase at that moment, from Connectix. With the acquisition, part of the staff from Connectix came to Microsoft, and, in 2004, Microsoft released Microsoft Virtual Server 2005.

Compared to the first version of Hyper-V, Microsoft Virtual Server is a dinosaur. That's not only because Hyper-V implements new features, but also because there is a major architectural difference between these products. This is the Hypervisor architecture.