How to understand cloud computing? Think of it like a food lover craving pizza...

You have certainly heard of three lofty concepts in Cloud Computing: IaaS, PaaS and SaaS. These terms are not easy to understand. However, if you are a foodie who loves pizza, the problem is easy to solve. Well, you may not actually be a foodie at all. The reason you call yourself one is really just to fish for compliments like "You eat so much and still stay so thin, I'm so jealous!" Or perhaps you just need a decent excuse for being a little plump.

How does a "foodie" get pizza?

1. Make it at home.

This is quite a hassle. You need to prepare many things: leavening dough, making the dough, putting it in the oven... To put it simply, you need everything shown in the image below:

2. Buy ready-made pizza and bake it at home.

You just need to buy the finished product from a pizza shop, bake it at home, and eat it at your own table. Unlike making it yourself, you need a pizza supplier.

3. Call for delivery and have pizza brought to your door.

Make a phone call and pizza is delivered to your doorstep.

4. Eat pizza at a pizza shop.

You don't need to prepare anything. Even the table belongs to the pizza shop.

To summarize, a foodie can get pizza through the following methods:

Now, forget about pizza!

Suppose you are a highly capable technology company that needs no external services. You own the infrastructure, applications, and everything else. You divide them into three layers: infrastructure, platform, and software, as shown below:

These are the three layers of Cloud Computing: infrastructure at the bottom, platform in the middle, and software at the top, namely Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS), and Software-as-a-Service (SaaS). Other "soft" layers can be added on top of these.

Your company has everything. This current state is called On-Premises deployment, just like making pizza at home. A few years ago, if you wanted to run enterprise applications in your office or on your company website, you needed to buy servers or other expensive hardware to run local applications and keep your business going. That is On-Premises deployment.

Suppose one day your boss has an epiphany: why make pizza yourself just to eat it? So they consider a cloud service provider. What services can this provider offer? The cloud services available correspond to the three layers of Cloud Computing: IaaS, PaaS, and SaaS, just like a pizza shop offering three options: buy and bake at home, delivery, and dine in.

Illustrated in a single diagram:

Now let's talk about the specifics.

IaaS: Infrastructure-as-a-Service

With IaaS, you can outsource hardware to an external provider. IaaS companies provide off-site servers, storage, and networking hardware that you can rent. This saves maintenance costs and office space, and your company can use this hardware to run its applications at any time.

Major IaaS companies include Amazon, Microsoft, VMWare, Rackspace, and Red Hat. Each has its own specialties. For example, Amazon and Microsoft offer more than just IaaS; they also rent out computing power to host your website.

PaaS: Platform-as-a-Service

The second layer is PaaS, sometimes also called middleware. All of your company's development can take place on this layer, saving time and resources.

PaaS companies provide various online solutions for developing and distributing applications, such as virtual servers and operating systems. This saves hardware costs and facilitates collaboration across distributed teams. Services include web application management, application design, application virtual hosting, storage, security, and application development collaboration tools.

Major PaaS providers include Google App Engine, Microsoft Azure, Force.com, Heroku, and Engine Yard. Newer entrants include AppFog, Mendix, and Standing Cloud.

SaaS: Software-as-a-Service

The third layer is SaaS. This is the layer you interact with daily, mostly accessed through a web browser. Any application running on a remote server that can be accessed over the network qualifies as SaaS.

The services you consume are accessed entirely from the web, such as Netflix, MOG, Google Apps, Box.net, Dropbox, or Apple's iCloud. Although these web services are used for business, entertainment, or both, they are all part of cloud technology.

Some SaaS applications for business include Citrix's Go To Meeting, Cisco's WebEx, Salesforce's CRM, ADP, Workday, and SuccessFactors.

Source: 51CTO.com