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IT Essentials — Assessing Infrastructure and Networks

A server is a computer program or device that provides functionality for other programs or devices,
called clients. Different types of servers include web servers, database servers, file servers, print
servers, and application servers, among others. Also commonly referred to as a server is the actual
hardware (physical computer), which is generally a powerful computer with the capabilities of
processing large amounts of data and often dedicated to a specific business function, such as the
organization’s email, files, applications, and/or website. In the general business context, a server
may describe the software or the hardware, but more likely, it describes the combination of the two,
as both are needed to provide functionality.

The most common servers today run either Microsoft’s proprietary Windows OS, IBM AS/400, or
Linux, a modifiable open source OS. The next slide will display graphics that compare Linux to
Windows.

Linux and Windows Operating Systems

The table below describes various characteristics of the two operating systems.

Virtualization

Virtualization is the process of configuring a computer system in an environment that is separate
from the actual hardware. Prior to the concept of virtualization, all OSs were installed on the actual
computer hardware, and that computer could only run one OS. With the concept of virtualization,
the virtual machine (VM) OS runs on the computer hardware, and multiple virtualized OSs can run
under the control of that VM. Common computer resources such as servers, desktops, and storage
devices can all be virtualized. VMs can be used for targeted purposes and discarded once that use
has been fulfilled.

A virtualized environment is usually accomplished by installing and using specialized software
(called a hypervisor) on the host machine that emulates a virtualized environment. A hypervisor is a
specific software set that creates and runs VMs and is known as a virtual machine monitor/manager
or VMM. There are two types of hypervisors: Type 1, which runs directly as the OS on the host
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