Cloud Computing Overview By Mithilesh Joshi

Cloud Computing provides us a means by which we can access the applications as utilities, over the Internet. It allows us to create, configure, and customize applications online.

What is Cloud?

The term Cloud refers to a Network or Internet. In other words, we can say that Cloud is something, which is present at remote location. Cloud can provide services over network, i.e., on public networks or on private networks, i.e., 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.

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:
  • Deployment Models
  • Service Models


Deployment models define the type of access to the cloud, i.e., how the cloud is located? Cloud can have any of the four types 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, e.g., 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.


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 (IaaS)
  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:


IaaS provides access to fundamental resources such as physical machines, virtual machines, virtual storage, etc.


PaaS provides the runtime environment for applications, development & deployment tools, etc.


SaaS model allows to use software applications as a service to end users.


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:


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.
  • 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:


    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.


    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.


    This risk involves the failure of isolation mechanism that separates storage, memory, routing between the different tenants.


    In case of public cloud provider, the customer management interfaces are accessible through the Internet.


    It is possible that the data requested for deletion may not get deleted. It happens because either of the following reasons:
    • Extra copies of data are stored but are not available
    • Disk destroyed also stores data from other tenants.


    There are four key characteristics of cloud computing. They are shown in the following diagram:


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.


Since Cloud Computing is completely web based, it can be accessed from anywhere and at any time.


Cloud Computing allows multiple tenants to share a pool of resources. One can share single physical instance of hardware, database and basic infrastructure.


It is very easy to scale up or down the resources at any time.


It is possible to monitor the resources which were used by the customers and currently assigned to customers.
Service Models & Deployment Models are described in above section.

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