Virtual Appliances and the Open Virtualization Format

“Let’s start with a quick discussion of the key behind virtual
appliances: the virtualization platform. Although operating systems
represent a virtualization platform for applications (sharing
access to the processor and resources), hypervisors do the same
thing for operating systems. Hypervisors are important, because
they allow you to run multiple, different operating systems on the
same system. From the perspective of a desktop user, this ability
is important, because it allows them to run Windows and Linux
concurrently. But from the perspective of a server, it permits
hosting multiple operating systems running a variety of server
applications concurrently (such as Web servers, e-mail
applications, databases, and other useful services). Further, each
operating system is isolated from one another, so a fault in one
does not affect any other.”

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