This document discusses virtual computing and virtual machines. It begins by defining virtual machines as isolated partitions within a computer that allow different operating systems to run simultaneously. Virtual machines prevent applications from interfering with each other and isolate crashes. The document then covers the history of virtual machines, how they function, advantages like consolidation and migration, risks, and characteristics of on-demand access and resource pooling. It provides examples of virtual machine monitors, paravirtualization, and deployment models like public and private clouds.

1. Personal Computer Application
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3. Virtual Computing / Virtual Machine
One instance of an Operating System along with one or more applications running in an
isolated partition within the computer. It enables different Operating System to run in the
same computer at the same time.
Virtual computing or Virtual machine (VM) are also widely used to run multiple instances of
the same Operating System, each running the same set or a different set of applications.
The separate VM instances prevent applications from interfering with each other. If one app
crashes, it does not affect the programs in the other VM. This approach differs from a dual
– boot or multi – boot environment, in which the user has to choose only one OS at startup.
All virtual machines in the same computer run simultaneously.
VMs are like Machines within the Machine
Each virtual machine functions as if it owned the entire computer. The Operating System in
each VM partition are called “guest Operating System,” and they communicate with the
hardware via the Virtual Machine Monitor (VMM) control program. The VMM “Virtualizes”
the hardware for each VM.
History
VM the first virtualized OS for IBM (International Business Machine) mainframes. VM runs
multiple IBM OS of any type, each with their own applications. Originally developed by a
separate research arm of the company, VM later became mainstream in the 1970s. In 2000,
IBM introduced z/ VM for the 64-bit z/ architecture.
Virtual Machine – Control Program and
Conversational Monitor System
VM – Control Program (VM-CP) is the “hypervisor” that provides the virtual machine
functionality. Conversational Monitor System (CMS) is a compact guest OS that is widely
used with VM to provide interaction for one user. Each user communicates with CMS in a
separate virtual machine in the computer.

4. Non-Virtual Versus Virtual
This shows three applications running in a regular computer versus a virtualized computer.
In the VM example, the guest operating systems may be the same or different.
Paravirtualization and Hardware
Guest operating systems can run in a virtual machine with or without modification. If changes
are made to the OS to recognize the VMM, it is said to be "paravirtualized." For example,
Linux and various Unix versions have been paravirtualized to run in the Xen VM
environment. However, if the CPU hardware supports virtualization, Xen can run guest
operating systems unmodified. In 2004 and 2006, Intel and AMD added virtualization to their
CPUs, which traps the calls to the x86 hardware, making it easier to develop VMMs that run
ordinary non-paravirtualized guest operating systems (see hardware virtualization).
Advantages of Virtualization
1 - Consolidation
Multiple operating systems can run in the same server, eliminating the need to dedicate a
single machine to one application. Old and new applications can run simultaneously with
their respective operating systems in multicore servers with many threads of execution,
saving space and power consumption in the datacenter. New versions of an OS and new
applications can be deployed without purchasing new hardware.
2 - Stability and Security
Conflicts can arise between supposedly stable applications, and troubleshooting can be
daunting. As a result, cautious system administrators often host each type of application in

5. a separate server even if the server is grossly underutilized. Multiple virtual machines
running bread and butter applications are kept safely separated from each other. In addition,
since each VM is isolated from the rest, a security breach in one does not affect the others.
The fault tolerance and security brought about by the isolation of each virtual machine is a
major benefit of virtualization.
3 - Development Flexibility
A virtualized computer can host numerous versions of an operating system, allowing
developers to test their programs in different OS environments on the same machine. In
addition, with each application running in its own virtual partition, crashing in one virtual
machine will not bring down the system.
4 - Migration and Cloning
Virtual machines, each with their own OS and applications, function like self-contained
packages that are said to be "decoupled from the hardware." It is relatively easy to move a
VM from one server to another to balance the workload, to migrate to faster hardware, as
well as to recover from hardware failure. VMs can be quickly cloned and deployed.
5 - Desktop Virtualization
An increasing trend is to store a user's desktop (OS and applications) in a separate virtual
machine in the server and use the PC or a dedicated terminal as a "thin client" to the server.
Each user is isolated from all other users due to the virtual machine technology, and the
maintenance of the applications is shifted from each user's desktop to the datacenter (see
thin client). See virtual machine monitor, virtualization, application virtualization and OS
virtualization.

6. What is Cloud?
Cloud computing provides us a means by which can access the applications as utilities, over
the internet it allows us to create, configure, and customize applications online.
The term Cloud refers to a Network or Internet. In other works, we can say that Cloud is
something, which is present at remote location. Cloud can provide services over network,
ex… on public or on private networks, ex… WAN, LAN or VPN.
Applications such as e – mail, web conferencing, customer relationship management (CRM),
all run in cloud.
What is Cloud Computing?
Cloud Computing refers to manipulating, configuring, and accessing the applications online.
It offers online data storage, infrastructure and application.
We need not to install a piece of software on our local PC and this is how the cloud computing
overcomes platform dependency issues. Hence, the Cloud Computing is making our
business application mobile and collaborative.

7. Basic Concepts
There are certain services and models working behind the scene making the cloud
computing feasible and accessible to end users. Following are the working models for cloud
computing:
i. Deployment Models
ii. Service Models
Deployment models
Deployment models define the type of access to the cloud, ex… how the cloud is located?
Cloud can have any of the four type of access: Public, Private, Hybrid and Community.
Public Cloud
The public cloud allows systems and services to be easily accessible to the general public.
Public cloud may be less secure because of its openness, ex… e – mail.
Private Cloud
The private cloud allows systems and services to be accessible within an organization. It
offers increased security because of its private nature.
Community Cloud
The community cloud allows systems and services to be accessible by group of
organizations.
Hybrid Cloud
The hybrid Cloud is mixture of public and private cloud. However, the critical activities are
performed using private cloud while the non – critical activities are performed using public
cloud.

8. Service models
Service models are the reference models on which the Cloud Computing is based. These
can be categorized into three basic service models as listed below:
1. Infrastructure As A Service (LAAS)
2. Platform As A Service (PAAS)
3. Software As A Service (SAAS)
There are many other service models all of which can take the form like XaaS, i.e., anything
as a Service. This can be Network as a Service, Business as a Service, Identity as a Service,
Database as a Service or Strategy as a Service. The Infrastructure as a Service (IAAS) is
the most basic level of service. Each of the service models make use of the underlying
service model, i.e., each inherits the security and management mechanism from the
underlying model, as shown in the following diagram:
Infrastructure AS A Service (IAAS)
IaaS provides access to fundamental resources such as physical machines, virtual
machines, virtual storage, etc.
Platform AS A Service (PAAS)
PaaS provides the runtime environment for applications, development & deployment tools,
etc.
Software AS A Service (SAAS)
SaaS model allows to use software applications as a service to end users.

9. History
The concept of Cloud Computing came into existence in 1950 with implementation of
mainframe computers, accessible via thin/static clients. Since then, cloud computing has
been evolved from static clients to dynamic ones from software to services. The following
diagram explains the evolution of cloud computing:
Benefits
Cloud Computing has numerous advantages. Some of them are listed below:
 One can access applications as utilities, over the Internet.
 Manipulate and configure the application online at any time.
 It does not require to install a specific piece of software to access or manipulate
cloud application.
 Cloud Computing offers online development and deployment tools, programming
runtime environment through Platform as a Service model.
 Cloud resources are available over the network in a manner that provides platform
independent access to any type of clients.
 Cloud Computing offers on-demand self-service. The resources can be used
without interaction with cloud service provider.
 Cloud Computing is highly cost effective because it operates at higher efficiencies
with greater utilization. It just requires an Internet connection.
 Cloud Computing offers load balancing that makes it more reliable.

10. Risks
Although Cloud Computing is a great innovation in the world of computing, there also exist
downsides of cloud computing. Some of them are discussed below:
SECURITY & PRIVACY
It is the biggest concern about cloud computing. Since data management and infrastructure
management in cloud is provided by third-party, it is always a risk to handover the sensitive
information to such providers. Although the cloud computing vendors ensure more secure
password protected accounts, any sign of security breach would result in loss of clients and
businesses.
Lock-IN
It is very difficult for the customers to switch from one Cloud Service Provider (CSP) to
another. It results in dependency on a particular CSP for service.
Isolation Failure
This risk involves the failure of isolation mechanism that separates storage, memory, routing
between the different tenants.
Management Interface Compromise
In case of public cloud provider, the customer management interfaces are accessible
through the Internet.
Insecure Or Incomplete Data Deletion
It is possible that the data requested for deletion may not get deleted. It happens either
because extra copies of data are stored but are not available or disk destroyed also stores
data from other tenants.

11. Characteristics
There are four key characteristics of cloud computing. They are shown in the following
diagram:
On Demand Self-Service
Cloud Computing allows the users to use web services and resources on demand. One can
logon to a website at any time and use them.
Broad Network Access
Since Cloud Computing is completely web based, it can be accessed from anywhere and at
any time.
Resource Pooling
Cloud Computing allows multiple tenants to share a pool of resources. One can share single
physical instance of hardware, database and basic infrastructure.
Rapid Elasticity
It is very easy to scale up or down the resources at any time. Resources used by the
customers or currently assigned to customers are automatically monitored and resources. It
make it possible
Measured Service
Service Models & Deployment Models are described in above section.

12. References
Web sites
Wikipedia
Tutorialpoint
Computer Desktop Encyclopedia
GCFLearning
Books & Magazines
Teachers Guide – Information and communication Technology (Grade – 12, 13)
Magazine – Computer Today
Magazine – TC Time
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