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The entire information technology industry is talking about the cloud these days. Many businesses are asking the fundamental question, what is cloud computing? And most importantly, how can I use it to make my business more competitive and better serve my customers? If youre struggling to understand cloud computing technologies, this tutorial will give you the background youll need to make wise adoption choices.

Before cloud computing, if you wanted some computational power, you had three choices:

Each of these models has pros and cons. If you bought the equipment, you typically owned it through the full depreciation cycle of three to five years. That might have been the cheapest option, but it was the least flexible. You gained some long-term flexibility when you leased the equipment, but you paid more in trade and you still had all the operations costs. Typically, you wouldnt lease equipment for less than a 3 month time horizon, and probably at least a year, otherwise the overhead cost of receiving, configuring, and then returning the equipment would be too high. Finally, if you rented the server, you could get something with granular, monthly terms, but you were far more limited in the hardware choices and you couldnt deploy it in your own data center. The upside was you might be able to have it up and running in as few as 24 hours from the time you placed the order.

These models form a continuum: on one side we have the buy-and-own-everything model; on the other side we have the own-nothing model. In the middle, we have a wide variety of models where some things are owned and others not.

In the simplest sense, cloud computing is merely a refinement of the own-nothing model, with shorter timescales for resource rental, and greater flexibility for the customer as a result. The National Institute of Standards and Technology (NIST) has created what has become the canonical definition of cloud computing, publication 800-145, titled The NIST Definition of CloudComputing.

NIST defines cloud computing as having five essential characteristics:

The five essential cloud characteristics define a cloud in terms of abstract characteristics and resources. The characteristics apply equally well to a low-level infrastructure cloud as to a high level application cloud. The NIST definition goes on to organize clouds into three cloud computing service models:

Finally, the NIST definition outlines four different deployment models:

The NIST service and deployment models form a matrix:

So, you can have a private IaaS cloud or a public PaaS cloud. Hybrid clouds are shown in the matrix, but they really are a mix of the various public, private, and community cloud types. Thus, you could construct an interesting hybrid cloud environment from a combination of a private IaaS cloud based on VMware, a public IaaS cloud based on Amazon EC2, and a public PaaS cloud based on Google AppEngine.

Most larger enterprises will create a hybrid cloud environment of some sort, with multiple public and private clouds, and possibly a community cloud thrown into the mix. Some clouds will provide enhanced security; others will provide enhanced performance; still others will offer optimized pricing. Enterprises will then deploy application workloads within a suitable cloud to create an optimized outcome. Management software will help match application workloads to the right clouds given optimization goals and risk and compliance restrictions.

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What is Cloud Computing? A Tutorial - Leverhawk