Virtualization allows a single computer to run multiple virtual machines simultaneously. This allows developers to easily create and restore test environments. It also enables demonstrators to maintain separate demo environments. Virtual machine snapshots can be easily saved and shared between computers, benefiting developers, demonstrators, and home users. However, virtualization performance declines as more virtual machines are run simultaneously on a single computer.

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Virtualization for Non-Hosted Applications
Introduction
Virtualization is the concept of using a program (the most popular is
called VMware) to allow one computer to “host” other computers on it.
These virtual computers, or virtual machines, can run applications
simultaneously with each other and with the host machine. The
program shares the host computer’s hardware and peripherals with each
virtual machine, so that each virtual machine acts as its own computer.
Historically, virtualization has been confined to the realm of large scale
servers and other hosted solutions. With faster and more efficient
desktops and laptops, which boast as much memory as servers did only
a few years ago, it is now possible to use virtualization outside of the
realm of hosted solutions and large scale server farms. Virtualization
has three major features: the fact that you can run multiple
environments on the same machine, the fact that you can take a
snapshot of an environment, save it, and restore back to that snapshot
extremely easily, and the fact that the snapshots are hardware
independent, allowing them to be shared between computers, even if
those computers have different hardware and peripherals.
Use of Multiple Environments on one Machine
One of the prime advantages of Virtualization is the ability for one
machine to act as a host to multiple additional environments. These
environments are completely separate from one another. There is no file
system overlap, no memory overlap, and the environments need not
even be the same operating system or the same type of operating
system. A Windows XP box can be used to host a Virtualized Linux
server, or a Windows Vista installation, or even something older, like a
Windows NT 4.0 installation.
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For a developer, this aspect
can be utilized to create any
number of test environments
for their applications. Without
it, the user would either have to
have dozens of extra
computers, or spend the time
and effort to install from scratch
multiple operating systems, just
to do his testing on. This could
take days or even weeks, time
which few developers have. If
a developer is working on
multiple applications, then he
can use virtualization to keep Figure 1 Virtualization can be used to maintain
his application development
separate security connections to different apps
environments on separate
simultaneously
machines, reducing the
possibility of conflict between them. If that developer is working
remotely, he may have firewall or other security concerns for logging into
remote client sites. These security restraints can often cause conflicts if
he tries to maintain more than one on the same computer. Virtualization
solves this problem by separating the security systems into each
individual environment.
For a salesperson or demonstrator, it allows his single laptop to act like a
multitude of servers, displaying how the application would work if it
utilized all of these separate servers for its enterprise, or it can show
different versions of the application, or even different localizations. In
addition, it can be used to display multiple applications, each one
operating independently on its own machine.
For the home user, virtualization can be used to create environments
which would otherwise be unavailable for specific applications. For
example, a Macintosh user can utilize VMware to create a Windows XP
VM and then use that machine to play certain Windows-only games on it.
The same can be done with a user who operates a Linux workstation. In
addition, a home user who wishes to learn more about Linux operation
and administration can setup a Linux VM on his Windows box, without
having to perform dual booting or re-partitioning of his hard drive.
But that’s only one feature of Virtualization.
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Ability to Easily Save and Restore Environments
VMware is one of the software packages available to perform
virtualization. One of its features is the ability to take a snapshot of an
environment. These snapshots are usually taken when the environment
is in a stable configuration, with no viruses or malware active. This is
obviously a boon to any user of a system, especially when they are in the
process of installing and configuring unknown software or immature
software. If the software installation fails, the user can restore back to
the previous snapshot and the user doesn’t have to worry about whether
the failed install correctly deleted any temporary files and removed any
extraneous registry Key. In addition, the saved environments can be
burned to a CD or stored in a tape backup system. This allows the
saved environment to be physically located off-site in case of disaster.
Developers can benefit from this feature as much as anyone else, as
they often install applications which might be charitably called
“immature”. If any of these applications spawn memory leaks or worms
or accidentally cause operating system problems, the developer is
secure in the fact that his system is easily restored.
Demonstrators usually don’t have to worry about unexpected changes to
their systems, so their dependence on this feature can be minimal. But
there is one aspect of this feature which can be a great benefit to them.
Sometimes demonstrations of a product include “destructive” changes.
For example, if the demonstration calls for certain data to be removed
from the database, either to show that the commands work properly, or
to demonstrate the products ability to handle loss of data. In this case,
the ability to easily restore an environment becomes a demonstrator’s
best friend. The demonstrator simply restores the environment to the
point it was before the demonstration began, and he’s ready for the next
demonstration.
Home users can benefit from this if their network isn’t that secure, or if
they have a habit of downloading “questionable” files which might contain
viruses or other malware. Or if they share their computers with kids who
might not be as responsible with their computer usage as they should be.
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Ability to Share Saved Environments
VMwares snapshots have almost universal portability. Since the
virtualization client handles interfaces to hardware elements and
peripherals, the shares can be moved from computer to computer with
very few portability problems. This can be helpful to users in many
ways.
Developers can use these saved environments for knowledge
management purposes. If the developer is moved from an application
and another developer takes over, the first developer can give the new
developer a snapshot of his current environment and the new developer
would be up and running immediately. Also, these saved environments
can be stored, so that if a developer is inactive on a project for a long
time, and then has to go back to that project (for example, if the client
elects to pay for an additional phase of implementation), he can easily
restore the environment to exactly where he was when the previous
phase was completed.
The developer can create demonstration environments that he can then
hand off to the demonstrators and sales people to use, secure in the
knowledge that these demonstration environments will work. And, if the
company uses Independent Validation and Verification, then the
developer can provide the testers with an environment that they can
easily test on. One that the developers are confident is valid and
doesn’t contain inconsistencies from the development environment or the
production environments. Demonstrators themselves can share
environments to allow the same presentations to be made in different
places at the same time.
Home users don’t have as many reasons to share environments. There
are some users who routinely setup other people’s machines and would
probably love to be able to use VM ware to quickly install a working
environment as easily as installing a VM, but until VMWare is widely
used by home users, such a thing probably won’t happen.
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Disadvantages and Limitations
Virtualization is not the be all and end all of computing, and there are
limitations to its abilities. One limitation is that a user can only run so
many independent VM’s on his desktop before the whole thing starts
running very slowly. Because each virtual machine acts and thinks like
its own separate machine, it can quickly eat up all of the available cycles,
especially on an older machine or a cheaper machine with fewer
capabilities. It obviously runs best on machines with multiple processors,
and requires lots of RAM and quite a bit of HD space. For the home
user, there are certain graphic intensive games that might not run on it or
might not run well on it. But with new computers getting faster and more
powerful every day, virtualization becomes a viable option for many
people who would otherwise never be able to afford multiple computers.
Conclusion
In conclusion there are many situations where virtualization is
not only appropriate, but can be a great time-saver to developers,
application demonstrators and salesmen, and even the advanced home
user. Virtualization does require the latest hardware, though, so it is not
something to be used lightly, but properly utilized, it can provide
flexibility, security, and convenience to these types of users. As laptop
and desktop computers become faster, and gain more and more
processers and more and more hard disk space, virtualization suffers
fewer and fewer limitations on its ability and users can get more and
more out of having the ability to host multiple environments on their
single computer.
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