Dissertaç ˜ao de Mestrado Mestrado em Engenharia Informática Jo ...

2. STATE OF THE ART AND RELATED WORK 2.1. Virtual Appliances
2.1.1 Virtualization
Virtual Appliance
JeOS
Virtualization Layer
Physical Hardware
Figure 2.1: Virtual appliance
Virtualization is a very broad term and refers to something which does not exist physically
but appears to exist. Think of it in the context of virtual reality. With virtual memory, for
example, computer software gains access to more memory than is physically installed, via
the background swapping of data to disk storage. Similarly, virtualization techniques can be
applied to other IT infrastructure layers such as networks, storage, laptop or server hardware,
operating systems and applications.
The concept of platform virtualization refers to the technique for hiding the physical char-
acteristics of computing resources from the way in which other systems, applications or end
users interact with those resources. In other words, virtualization allows multiple logical com-
puting units to run on a single physical computing unit, like in the Figure 2.2. This is done with
the aid of a software layer (alias virtualization layer, virtualization manager, virtual machine
monitor or hypervisor) which provides the illusion of a “real” machine to multiple instances of
“virtual machines”.
Virtualization Layer
Computational Unit
Figure 2.2: Physical unit running four VMs
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