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CompTIA A+ Certification All-in-One Exam Guide

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Server-Side Virtualization

When it comes to servers, virtualization has pretty much taken over

everywhere. Many of the servers we access, particularly Web and e-mail

servers, are now virtualized. Like any popular technology, virtualization

engrosses a lot of people continually working to make it better. VMWare

Workstation and VirtualBox are very powerful desktop applications, but they

still need to run on top of a single system that is already running an operating

system—the host operating system.

What if you could improve performance by removing the host operating

system altogether and install nothing but a hypervisor? Well, you can! This is

done all the time with another type of powerful hypervisor/OS combination

called a bare-metal hypervisor. We call it bare metal because there’s no other

software between it and the hardware—just bare metal. The industry also

refers to this class of hypervisors as Type-1, and applications such as

VMware Workstation as Type-2 (see Figure 22-23).

Figure 22-23 Type-1 versus Type-2 hypervisors

In 2001 VMware introduced a bare-metal hypervisor, originally called

ESX, that shed the unnecessary overhead of an operating system. ESX has

since been supplanted by ESXi in VMware’s product lineup. ESXi is a free

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