Cloud Computing

Poon Kwok Huen

Introduction
Cloud computing is a very popular concept applied in many internet websites and applications like Google and Facebook, but it seems that not many people what cloud computing is. Through cloud computing, users can just use their phones to connect to the internet and access software, platform and hardware provided by many other computers that are also connected to the internet. We can also perform computation of very large programs which even supercomputer takes time to solve with cloud computing.

Definitions
Actually, cloud computing is not a new technology, but only a concept about delivery of resources on internet. We can find many definitions of cloud computing on the internet and we may not have a clear idea about cloud computing, but we can still conclude some common characteristics and applications about cloud computing.

Cloud computing is to access internet resources by the users’ own internet devices and make use of the resources to do tasks. As internet is a very big collection of computers, cloud computing can also be described to be using the software and hardware resources of the other computers through internet. As we can gather the power of a large number of computers, we can perform powerful computing or provide computing services through internet.

Characteristics
In real life situation, cloud computing is used by large companies for delivering their services. They set up many powerful servers and develop applications for users to access, with some are charged and some are free of charge. This kind of service shares 3 properties:

1. The service is charged according to the amount of resources used, like the amount of time using the online service of the computation power used by the servers.
2. Users can use and cut the service as they want to, as well as they have no time limit or specified period. The providers put the services on their platform and users can use the service as they pay the required charge or cut the service by stop accessing the service.
3. The services provided are totally maintained by the providers, which are the companies. As the resources such as software and hardware are all owned by the companies, the companies are responsible to maintain the functionality of the resources so to maintain stable services.

These services are divided into 3 main types: Software-as-a-Service (SaaS), Platform-as-a-Service (PaaS) and Infrastructure-as-a-Service (IaaS).

Software-as-a-Service (SaaS)
SaaS is to provide software for user to use online. Originally, individual users or companies need to buy the license of software for several years in order to use the software, and they can install the software at their computer to do their tasks. Now cloud computing allows the user to use the software on demand. The software is installed in the providers’ servers. When the user wants to use it, they can connect to the providers’ servers and use the software online. It can reduce the cost of the software for users in a small scale, and the software is kept to be the most upgraded version. Also, the requirement of hardware for the users’ computers is not high as they just need their device to connect to the computer, operate the software and receive the result, but not computing the content. Nowadays SaaS is focusing on commercial software, and some companies such as Salesforce are fighting for the SaaS market.

Platform-as-a-Service (PaaS)
PaaS is to provide a platform, including a set of software on an API, website portals or gateway software, for users to develop their own set of programs on the platform. As a result, PaaS is an entire service for users to develop their own software which fits them most. Also because the users develop the PaaS, it helps the improvement of PaaS and SaaS, creating more functions and applications for the platform. For example, Google provided the Google App Engine in 2008 for users to develop their apps, which is also a typical case of PaaS.

Infrastructure-as-a-Service (IaaS)
IaaS is to provide users with all the server resources, including start, stop, access, configure, storage, computing power, internet service and software. It is just like using a virtual machine online and you can do whatever you want. Base on the concept of on demand, a user can just use what he or she needs and leaves the other resources, so that the other resources for other usage. The most famous IaaS provider is Amazon EC2, which start running from 2006 and provide virtual machine with different configurations.
 

Conclusion
There are still many probabilities for cloud computing. The characteristics, definition and common service form stated above are just some brief introduction about the situation and application of cloud computing and the whole world is still looking forward to how cloud computing can lead the development of the commercial world, electrical world and our living standard.

References

1. “What is Cloud Computing?” http://searchcloudcomputing.techtarget.com/