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VIRTUALIZATION AS A TOOL TO SUPPORT THE AVAILABILITY OF COMPUTER 
NETWORKS IN CASE OF CONTINGENCIES AND DISASTER RECOVERY 
 
Andréa Martins Cristóvão – UNIP – she_ra@uol.com.br 
Ivanir Costa – UNIP – icosta@terra.com 
João Carlos Nogueira Guirau – UNIP – jcguirau@blocktime.com.br 
Roberto Aures A. Moura – roberto.aures@terra.com.br 
 
Abstract: The IT challenge is to continue producing devices smaller, lighter and faster and at the same 
time, find better ways to manage the complexities of IT solutions involved. The IT industry drives a 
huge effort to security and information management for the production of more flexible systems to make 
them available to users anytime, anywhere. This need arises virtualization is an abstraction layer that 
separates the operating system hardware in order to provide mobility and optimize the utilization of 
information technology. The concept of this new platform paves the way for powerful devices, 
autonomous and reliable. The aim of this study is to analyze the benefits of this new technology and the 
impact of virtualization in the process of contingency and disaster recovery. To this end, we conducted a 
literature search - to understand the concepts underlying the areas of virtualization and security - 
conducted a survey with 25 companies to verify the possibility of implementing virtualization solutions 
as a contingency and the benefits this process can offer for companies, and a case study, which assessed 
the process for using this technology. Thus it was possible to analyze whether the advantages of this 
technique are really tangible in the current scenario, and also the benefits that has shown in the 
contingency and disaster recovery. The results of this study will serve as a basis for further field 
researches. 
Keywords: Platform Virtualization; VMWare; Security; Contingency. 
 
Introduction 
 
 Virtualization is a simple way to create systems that divide the sub-systems in devices more 
manageable. Thus, it tends to provide more security to the system, network and applications, because 
isolation of potentially vulnerable sub underlying systems and other virtual platforms. 
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Virtualization can be defined as "a technique that combines or divides computing resources to 
provide one or more operating environments for implementing" [NandaChiueh, 2005]. The 
environments created by this technique are called virtual machines. 
Among the concepts involved in the study of virtual machines, a monitor (also called a hypervisor, 
VMM, or Virtual Machine Monitor) is a key. 
The monitor is a software layer inserted between the system visitor (guest system) and hardware 
system where the visitor performs. This layer is an interface between the systems potential visitors 
(virtual) and the hardware that is shared by them. She is responsible for managing all hardware 
structures, such as MMU, device I/O, DMA controllers, creating a complete environment (virtual 
machine), where visitors systems run [XenSource, 2008]. 
 Platforms virtualization can be defined as the creation of a computer system logically segmented, 
which runs on a real basis. The virtual platforms are seen by the User and act as if they were physical 
machines. Because they are abstract and divided from bases hidden, the virtual platforms are easily 
transportable and robust. 
The virtualization allows you to create multiple virtual machines with heterogeneous operating 
systems running in isolation, side by side in the same physical machine. Each virtual machine has its 
own virtual hardware (e.g. RAM, CPU, etc), on which the operating system and applications are loaded. 
With virtualization we can run multiple operating systems on an underutilized server or 
workstation. You can easily consolidate multiple platforms running on different operating systems and 
heterogeneous applications into a single, powerful and reliable platform. 
The concept of virtualization includes all sections of the platform – from applications and 
operating systems – components, processors and interconnections of the platform. 
 
1. Classification of Virtual Machines 
 
According to [King, 2003], VMMs can be classified in several ways. One refers to how close the 
interface they provide is the underlying hardware. 
VMMs as VMware ESX Server and emulators such as Bochs have a hardware abstraction 
identical to the underlying hardware. To arrive at a level of abstraction so high, some monitors fall 
within the guest OS (host OS) device drivers that will be used by guest operating system (guest OS) by 
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the VMM. Still others VMMs have a different interface from the underlying hardware. The Java virtual 
machine architecture is a fully independent of the hardware on which you run. 
Another VMMs classification refers to the platform on which they run. According to this 
classification, virtual machines can be of two types [King, 2003]: 
• Type I - The VMM is implemented directly on the underlying physical hardware. The VMMs 
Xen and VMware ESX Server are examples of such virtual machines. 
• Type II - The VMM is implemented completely on the host operating system. Examples of 
such virtual machines are VMware Server VirtualPC. 
 
2. Virtualization and Abstraction 
 
In contrast to abstraction, virtualization does not necessarily aims to simplify or hide 
implementation details of systems and components. 
A virtualization software uses the abstraction of a file as an intermediate step to identify the 
necessary mapping between virtual disks and real. 
One write to the virtual disk is converted to a write to the file and, therefore, in a real disk write. 
The detail provided in the virtual interface is no different from addressing the real disk and there is no 
abstraction on the virtual disk. 
According to the web site NextG (2008), the virtualization of a system or component, such as a 
processor or memory, at a certain level of abstraction maps its interface and features visible on another 
interface and features of an underlying real system. 
Therefore, the virtual system appears as if it was real, or even several virtual systems. The virtual 
system can be equal to the real system or, possibly, the mapping can create different features for the 
interface and the virtual resources. 
The concept of Virtualization includes all sections of the platform – from applications and 
operating systems – components, processors and interconnections of the platform. 
 
3. Virtualization and Emulation 
 
Emulation is the recreation of a working environment free from any necessary relationship to the 
environment-host and without hardware assistance, while virtualization lets you create many virtual 
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machines. A less obvious use of virtualization and emulation is the development of software. The 8-bit 
games were developed on robust computers, because this made it easy to monitor the operation 
instruction by instruction. Developing directly on the desired platform was almost impossible (NextG, 
2008). 
But long ago, computers represent a platform self-sufficient and low cost for development. And, 
we got to the point where a micro-computer can simulate itself fast enough for normal use. Today, the 
development tools can climb another step of quality and complexity. 
According to the web site NextG, a company in Silicon Valley claims to have achieved one of the 
main goals pursued in the technology industry: an almost universal emulator that allows you to run 
software developed for a given platform, in any other, with virtually no declines in performance. This 
includes Macs, PCs and various types of mainframes and servers. 
 According to company’s executives, an universal computer emulator is to informatics as the 
transformation of metals into gold was to alchemy. 
Many have tried, all failed. They explain that, although various schemes limited emulation have 
been successful – Apple'stransition to the PowerPC platform and transmutation code for the x86 
architecture made by Transmeta – no one has developed an emulator for processors and operating 
systems. 
The software was initially developed at Manchester University (United Kingdom) by a professor 
of computer science Alasdair Rawsthorne. One of the most important innovations is the intermediate 
representation, a kind of common language, which gives the software the flexibility to translate from 
one platform to another. 
The difference between emulators and virtual machines is basically the level of abstraction. While 
in an emulators all instructions are conventionally translated and interpreted, in the virtual machine 
instructions are executed in the most native possible. 
 Emulators can be classified in several ways. According to its nature of use, it can be classified as 
(Laureano, 2006): 
• Processor emulators. 
• Operating systems emulators. 
• Specific hardware platform emulators. 
• Videogames emulators (consoles). 
 
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4. Evolution of Virtualization 
 
According to Nanda and Chiueh (2005), there are multiple storage virtualization technologies that 
have evolved, including solutions for internal and external bandwidth (in-band and out-band) based in 
storage and hosting. The first virtualization technologies that emerged were based solutions in storage. 
They allow multiple servers to share access to data in a single array variable that stores a set of values of 
the same type. The negative side, however, is that these servers can not access the data beyond its own 
array. In addition, users are in danger of being limited to solutions that rely on the manufacturers, based 
on the constraints of hardware compatibility wider array of servers or directly connected. Virtualization, 
based on storage, can then be more expensive than alternatives of lower priority. 
In other hand, hosting based solutions enable the allocation of various disk arrays, from various 
manufacturers, present themselves as a virtual group to a single server host. This enables greater 
flexibility to enable them to be completely independent of manufacturers of storage solutions, but still 
enjoy the benefits of centralized storage management from a single console. Although the data are 
concentrated to access only through a single server, this can become highly available, ensuring the use 
of data. A potential disadvantage of this solution arises when multiple servers require shared access to 
the same data. Thus, we can consider the duplication of data or other methods of storage virtualization. 
The architecture in-band inserts the device virtualization in the data network between the host and array. 
These devices offer volume management and other additional features such as data movement and copy 
service. He makes the replacement controllers for the storage devices that have being virtualized (Nanda 
and Chiueh, 2005). 
The first advantage of this approach is simplicity. A new device itself can be developed to act as a 
central point of management for multiple systems connected. The recent appearance on a large scale, of 
monolithic arrays of high performance devices in-band virtualization, shows that advantage. 
At one precise point, for large environments, even the strategy of scale may prove insufficient and 
will be need to develop a new in-band appliance. Each of these devices has responsibility for separate 
areas of virtualization, resulting in the need to manage independent pools of Virtualization. The 
consequence can leverage the original benefits of reducing complexity and simplifying of the 
management provided by virtualization. 
 
 
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5. Benefits of Virtualization 
 
 The bet in Virtualization solutions derives from the need of the Information Technology managers 
to give an effective response to the increasing number and range of computing environments within 
organizations. Moreover, the proper management of the TCO – Total Cost of Ownership is more than 
ever relevant, as well as the ability to resolve the growing difficulties of maintenance and management 
of those environments. 
Virtualization infrastructure provides abstraction from the various methods of computation as 
processing, data storage, network and software. By implementing this concept, are eliminated physical 
constraints and resources are available as "logical groupings”, which can be used anytime and anywhere. 
The application of intelligent storage software virtualization layer provides a means of resolving 
functional challenges of storage, without compromising the need for data availability. It allows an 
unprecedented degree of flexibility in the use of storage resources to meet requirements relating to 
applications and end users, 
The virtual storage devices are not restricted to the limitations of capacity, speed or reliability of 
the physical devices that include them. The Provisioning means to provide users or applications the 
amount and best type of storage, at the right time. Virtualization makes this process much easier. 
Combined with centralized administration, allows changes in the physical storage layer to be done 
without interrupting access to data in order to provide uninterrupted, high quality storage services in real 
time. 
The Virtualization should revolution the way to manage applications, security and storage in the 
companies, converging systems to a single point, facilitating the maintenance and control of the 
network. Therefore, its benefits go through the centralized management of all storage, better access to 
users and applications, reducing training costs, easiness administration, reduced physical storage costs, 
eliminate downtime, greater scalability and capacity allocation on demand. 
According to IDC, virtualization is in the way to become a standard practice among the thousand 
largest companies in the world, listed in the Fortune 1000. According to Forrester Research, more than 
40% of U.S. companies have already embraced the technology. 
The virtualization software allocates the hardware resources as processing, memory and storage, 
that will be assigned to each virtual station, and allows to reallocate these resources in accordance with 
the demand of each application in determined moment of the company. 
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With the virtualization it is possible to keep virtual stations running redundant applications, 
allowing that, in the case of environment fail, the other is used as contingency resource. With the 
support of appropriated software, it is still possible to move different virtual stations to different 
hardware in case of a physical problem, thus preventing the loss of productivity. 
In accordance with data given by VMware, the virtualization, combined with the consolidation of 
servers, reduces in up to 53% the costs with the hardware and 79% the operational costs, generating an 
average economy of up to 64% for the company who adopts the solution. 
 
6. The process of virtualization as a contingency 
 
To assess whether the process of virtualization can be used in small businesses, a survey was 
conducted with 25 SME - Small and Medium-Sized Enterprises, established in São Paulo. 
The companies surveyed have between 1 and 6 servers and up to 120 computers in a network, in a 
total of 49 servers searched. 
In the survey it was found that 72% of companies surveyed have 1 single server running users 
authentication services, file sharing, email and database management system (DBMS), also that 65% of 
server processors surveyed have the capacity to support the process of virtualization Type I, i.e., that 
supports the virtualization process implemented directly on the hardware, and that 30% of the servers 
support the process of Type II virtualization, implemented on the native operating system. 
About the contingency, 52% of servers have mechanisms for fault tolerance in hard drives; in allcases, servers have backup routines of the data, and 60% of cases are being used tape drives, removable 
type DAT, LTO or removable cartridges and 40% in external hard drives. It was also found that 70% of 
the servers take up to 6 hours to carry out their daily backup routine. Only 10% of the companies keep a 
copy of your information stored outside of the main work environment. 
We note also that the average utilization of processors installed on the servers tested, in 65% of 
cases did not exceed the average use of 30% of installed capacity. 
In this scenario, the study was conducted to evaluate the process of virtualization can be used as a 
tool for contingency and disaster recovery, reducing downtime for network access of computers and 
their systems. 
It was selected a company where all data were stored on a single server where we adopted the 
implementation of a process of converting physical to virtual server, known as P2V, using the VMWare 
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Converter program, which creates a copy of the hard disk partitions to an external drive, transforming 
the content of hard disks in files. 
This process took approximately 6 hours for a server with a 75GB hard drive. These files were 
transferred to a microcomputer equipped with the VMWare Player program, where tests were 
performed, noting the availability of the server entirely in a test environment. 
In experimentally way, it was evaluated the recovery process of this same server, using the current 
procedures for data retrieval, i.e., installing the native system, the installation of their applications and 
the recovery of stored backup files. The duration of this process was 10 hours when, during this time, 
the network was unavailable. 
It was performed the same procedure to recover the server using the server created by the process 
of virtualization and the data were recovered from the previous day in about 2 hours, i.e., it was found 
the reduction of the downtime of the system by 80%. Another advantage that was shown is that the 
server created by virtualization process could be removed from the company in an external disk, thus 
providing a new tool for contingencies outside the company. 
 
7. Conclusion 
 
The study, which was based on literature review and case study, has showed that virtualization has 
many advantages, despite a high initial cost, for the purchase of equipment which generates for the 
company a charge bigger than a common system. 
The need to reduce energy consumption and the search for technological innovations that make 
better use of existing IT resources, brought the process of virtualization for the current scenario of 
business. 
The falling costs of virtualization programs, which are up to made available at no cost to users, 
presents new conditions for their use in large scale, including SME – Small and Medium-Sized 
Enterprises (businesses), previously excluded from this process by the high costs involved. 
The use of virtualization as a contingency in the computer networks of small size, offers facilities 
for this environment to be endowed with the same conditions of security and high availability offered to 
large corporations. 
The hiring of servers in data centers with lower values, offers facilities for that SME – Small and 
Medium-Sized Enterprises (companies) to review their investments in technology, reaching the 
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conditions to maintain a copy of your computing environment in a out side environment and with 
security. 
 
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on System Science 2003. 
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Tipo de Produção: Anais (meio digital) 
 
 
Título do Texto: Virtualization as a Tool to Support the Availability of Computer 
Networks in Case of Contingencies and Disaster Recovery 
Autores: A. M. Cristóvão, I. Costa, J. C. N. Guirau, R. A. A. Moura 
 
 
Título do Meio de Publicação: International Conference on Society and Information 
Technologies (ICSIT) 
 
 
Local da Publicação: Orlando - EUA 
Mês e Ano da Publicação: 2010 
URL: www.icsit.com 
 
 
Série: 1 
Volume: 1 
Nº do Fascículo: 1 
 
 
ISBN: 9781934272855 
 
 
Área de Concentração: Gestão de Sistemas de Operação 
Linha de Pesquisa: Redes de Empresas e Planejamento da Produção 
Projeto de Pesquisa: Processos de Desenvolvimento e Operação de Sistemas de Informação 
 
 
 
O conteúdo deste trabalho é de responsabilidade do(s) autor(es).