Cloud Computing: What is Cloud, Cloud based Computing?

   

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What is Cloud computing?
To understand what is Cloud computing, one needs to understand why its actually required. A small company decides to use Microsoft outlook to facilitates its internal communications. This company will require to procure required Hardware and software, do the setups, maintian the Software and decdicated IT team to support the Email client incase of any issues. What if the Company decided to use Gmail instead, in that case they don't need any Hardware(Servers), software to be installed on Computers and no IT Team required. All the company needs to do is provide acces to GMAIL to each of its users. 

Cloud computing is a type of computing that relies on sharing computing resources rather than having local servers or personal devices to handle applications. In cloud computing, the word cloud is used as a metaphor for "the Internet," so the phrase cloud computing means "a type of Internet-based computing," where different services such as servers, storage and applications are delivered to an organization's computers and devices through the Internet.

 
Background of Cloud Computing:
Cloud computing is comparable to grid computing, a type of computing where unused processing cycles of all computers in a network are harnesses to solve problems too intensive for any stand-alone machine.A great example of how this technology is being used is SETI@HOME, SETI needs a lot of computational power to scan through all of its radio signal data to find intelligent signal. Buying that amount of computational power would be incredibly expensive, so SETI@home comes up with an absolutely ingenious way to create that computing power out of thin air. When your computer is idle, it displays a screensaver. In most cases, a computer displaying its screensaver is doing absolutely nothing. All the computing power available in your machine is being wasted. So SETI@home created its own screensaver, which you install on your machine. With the SETI@home screensaver installed, your computer actually processes SETI data when it is idle. The screensaver downloads a packet of data containing a work unit of radio signals and then grinds away on them. When it's done, it sends the results back and gets another packet. The screensaver, instead of displaying fish or flying toasters, displays the work in progress.

Distributed Computing Systems are of two types
 1. Cluster Computing: Collection of high-end computers having same OS, and similar Hardware
     (workstations/PCs) usually closely connected through a LAN.
 2. Grid Computing: Clusters of different Hardware/Software may be combined to form a "Grid“ of a
      massive computing power.

Types of Grids
 1. Computational Grid–Shared Compute Resources.
 2. Data Grid–Access to Large amounts of Data spread across various sites
 3. Collaboration Grid-multiple collaboration systems for collaborating on a common issue.
Grid Computing was an enabling technology and inspiration for Cloud Computing. Distributed systems tend to have distributed memory, so the most common programming model is Message Passing between the different nodes.The processes on a distributed system communicate by passing messages which can be either control or data messages.Message Passing Interface (MPI) is a standardized protocol and API for this type of model

Types of clouds:
There are different types of clouds that you can subscribe to depending on your needs. As a home user or small business owner, you will most likely use public cloud services.
1. Public Cloud: A public cloud can be accessed by any subscriber with an internet connection and access to the cloud space.
2. Private Cloud: A private cloud is established for a specific group or organization and limits access to just that group.
3. Community Cloud: A community cloud is shared among two or more organizations that have similar cloud requirements.
4. Hybrid Cloud: A hybrid cloud is essentially a combination of any of the above.

Type of Clouds based on the service:
1. Software as a Service: A SaaS provider gives subscribers access to both resources and
    applications. SaaS makes it unnecessary for you to have a physical copy of software to install on
    your devices. SaaS also makes it easier to have the same software on all of your devices at once by
    accessing it on the cloud.
2. Platform as a Service: A PaaS system goes a level above the Software as a Service setup. A PaaS
    provider gives subscribers access to the components that they require to develop and operate
    applications over the internet. It provides the required Platform for deploying your own Software
    applications into the Cloud.
3. Infrastructure as a Service: An IaaS agreement, as the name states, deals primarily with
    computational infrastructure. So it provides the required Hardware's and other infrastructure for
    your to establish the Platform and deploy your Software applications.