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<!DOCTYPE section PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
]>
<chapter id="chap-Virtualization_Getting_Started-Advantages">
<title>Advantages and misconceptions of virtualization</title>
<para>
There are many advantages to virtualization and perhaps an equal amount of misconceptions surrounding it. This chapter will explore these points.
</para>
<section>
<title>Virtualization costs</title>
<para>
A common misconception is that virtualization is too expensive to justify the change. Virtualization can be expensive to introduce but often it saves money in the long term. It is important to perform a Return on Investment (ROI) analysis to determine the best use of virtualization in your environment. Consider the following benefits:
</para>
<variablelist>
<varlistentry>
<term>Less power</term>
<listitem>
<para>
Using virtualization negates much of the need for multiple physical platforms. This equates to less power being drawn for machine operation and cooling, resulting in reduced energy costs. The initial cost of purchasing multiple physical platforms, combined with the machines' power consumption and required cooling, is drastically cut by using virtualization.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Less maintenance</term>
<listitem>
<para>
Provided adequate planning is performed before migrating physical systems to virtualized ones, less time is spent maintaining them. This means less money being spent on parts and labor.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Extended life for installed software</term>
<listitem>
<para>
Older versions of software may not run on newer, bare metal machines directly. However, by running the older software virtually on a larger, faster system, the life of the software may be extended while taking advantage of the performance from the newer system.
</para>
</listitem>
</varlistentry>
<!--<varlistentry>
<term>Buying new hardware to store data</term>
<listitem>
<para>
There is no need to buy more hardware to expand on storage space because everything is virtualized and only needs one physical system.
</para>
</listitem>
</varlistentry>-->
<varlistentry>
<term>Predictable costs</term>
<listitem>
<para>
A Red Hat Enterprise Linux subscription provides support for virtualization at the normal fixed rate, making it easy to predict costs.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Less space</term>
<listitem>
<para>
Consolidating servers onto fewer machines means less physical space is required. This means the space normally occupied by server hardware can be used for other purposes.
</para>
</listitem>
</varlistentry>
</variablelist>
</section>
<section>
<title>Virtualization learning curve</title>
<para>
A misconception exists that virtualization is difficult to learn. In truth, virtualization is no more difficult or easy to learn than any new process. The skills required for managing and supporting a physical environment are easily transferable to a virtual one. Virtual environments function similarly to their physical counterparts, ensuring the learning curve remains a slight one.
</para>
</section>
<section>
<title>Performance</title>
<para>
On older virtualization versions that supported only a single CPU, virtual machines experienced noticeable performance limitations. This created a long-lasting misconception that virtualization solutions are slow. This is no longer the case; advances in technology allow virtual machines to run at much faster speeds than previously.
</para>
</section>
<section>
<title>Disaster recovery</title>
<para>
Disaster recovery is quicker and easier when the systems are virtualized. On a physical system, if something serious goes wrong, a complete re-install of the operating system is usually required, resulting in hours of recovery time. However, if the systems are virtualized this is much faster due to migration ability. If the requirements for live migration are followed, virtual machines can be restarted on another host, and the longest possible delay would be in restoring guest data. Also, because each of the virtualized systems are completely separate to each other, one system's downtime will not affect any others.
</para>
</section>
<section>
<title>Security</title>
<para>
<!--While virtualized systems require a host for operations, this host is usually bare metal with few, if any network services. The host supporting virtualized machines requires few, if any, network services. This means that it is very secure and need only to set up Secure Shell (SSH) manually. This section will include an overview of the security available. -->
A virtual machine uses SELinux and sVirt to improve security in virtualization. This section includes an overview of the security options available.
</para>
<section>
<title>Virtualization security features</title>
<formalpara>
<title>SELinux</title>
<para>SELinux was developed by the US National Security Agency and others to provide Mandatory Access Control (MAC) for Linux. Under control of SELinux, all processes and files are given what is known as a <emphasis>type</emphasis>, and access is limited by fine-grained controls. SELinux limits the abilities of an attacker and works to prevent many common security exploits such as buffer overflow attacks and privilege escalation.</para>
</formalpara>
<para>SELinux strengthens the security model of Red Hat Enterprise Linux hosts and virtualized Red Hat Enterprise Linux guests. SELinux is configured and tested to work, by default, with all virtualization tools shipped with Red Hat Enterprise Linux 6.</para>
<note>
<para>For more information on SELinux, refer to the SELinux documentation at <ulink url="http://docs.redhat.com/docs/" />. For specific details on the relationship between SELinux and virtualization, refer to the <citetitle>Red Hat Enterprise Linux 6 Virtualization Administration Guide</citetitle>.
</para>
</note>
<formalpara>
<title>sVirt</title>
<para>sVirt is a technology included in Red Hat Enterprise Linux 6 that integrates SELinux and virtualization. It applies Mandatory Access Control (MAC) to improve security when using virtual machines, and improves security and hardens the system against bugs in the hypervisor that might be used as an attack vector for the host or to another virtual machine.</para>
</formalpara>
<note><para>For more information on sVirt, refer to the <citetitle>Red Hat Enterprise Linux 6 Virtualization Administration Guide</citetitle>.</para></note>
</section>
</section>
<section>
<title>Virtualization for servers and individuals</title>
<para>
Virtualization is not just for servers, it can be useful for individuals as well. Desktop virtualization offers centralized management, an improved desktop solution, and better disaster recovery. Using connection software it is possible to connect to a desktop remotely.
</para>
<para>
For servers, virtualization is not only for larger networks, but for any situation with two or more servers. It provides live migration, high availability, fault tolerance, and streamlined backups.
</para>
</section>
<!--<section>
<title>Rackspace</title>
<para>
By consolidating servers onto fewer machines, less physical space is taken up. This can mean the space normally taken up with server hardware can be used for something else, be it new systems or even just storage space.
</para>
</section>-->
</chapter>
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