This chapter covers all the basics of the vSphere architecture, virtualization, an introduction to hypervisors, and virtual infrastructure.
We will cover the following topics:
Understanding the need for, and use of vSphere and how it differs from other common hypervisors
Understanding ESXi and modes of management
History of ESXi
Different types of vSphere installations: Auto Deploy, fresh installation, and upgrade
Introduction to virtual infrastructure: virtual machines, disks, CPUs, memory, switches, network, and storage
Let us start with understanding the virtualization philosophy. Virtualization is the separation of a resource or request for a service from the underlying physical delivery of that service. In other words, it's an abstraction of the operating system from hardware resources present on your server.
This blend of virtualization provides a layer of abstraction between computing, storage, and network hardware, and the application running on it. This implementation of virtualization is invisible to the end user as there is very little change to the end user experience.
The key benefit of server virtualization is the ability to run multiple operating systems on a single physical server and share the same underlying hardware resources. Virtualization has been a part of the IT industry for decades, but in 1998, VMware, Inc. delivered the benefits of virtualization to industry standard x86-based platforms.
There are two approaches to server virtualization:
Hosted approach: A hosted approach provides partitioning services (virtualization) on the top of a standard operating system (for example, Microsoft Windows 7) and supports the broadest range of hardware configuration, as it uses the drivers of the underlying operating system. This design is also called Type 2 hypervisor. Popular products in this category are VMware Workstation and VMware Player. Comparable competitor products include Oracle VirtualBox and Parallels Desktop.
Bare-metal (hypervisor) architecture: A hypervisor architecture is the first layer of software installed on a clean x86-based system. Hence, it is often referred to as the bare-metal approach. Since it has direct access to the hardware resources, a hypervisor is more efficient than hosted architectures. This enables greater scalability, robustness, and performance. VMware vSphere (ESXi) is one of the pioneers in bare-metal architecture. Bare-metal hypervisors are also called Type 1 hypervisors.
The following image shows differences between the two major virtualization approaches:
