The definition of cloud computing is about as hazy as the name itself and different people try to give different meanings to cloud computing. I’ve found that any definition I come up with is countered by someone else’s definition.
So let me put it this way: cloud is about consuming I.T. services in ways other than traditional on-premises infrastructure. It involves connecting users to business applications through the internet, and there are a wide variety of usage models ranging from system ownership to utility-like on-demand delivery.
You can think about cloud with a car metaphor. You can own your car and be fully responsible for its operation and maintenance—that’s like traditional I.T. or private cloud.
Or you can lease a car, letting someone else maintain it for a fixed fee and you return it at the end of the lease—that’s like managed services.
Or you can take a taxi, paying for only for the mileage and time that you use, and when you’re done, someone else uses the taxi. And if you have a lot of people to transport, you take multiple taxis—that’s like cloud services.
Or you can take a public bus for a flat fee, going where it’s headed, along with everyone else riding along—that’s like software-as-a-service.
From a business sense, cloud is about moving from an I.T. systems-centric information technology to a services-centric business system where you enjoy flexible and agile I.T. services.
Let’s quickly review the fundamental cloud business models: public cloud, private cloud, software as a service, and hybrid cloud.
With a public cloud, you are renting compute and storage capacity from a large I.T. infrastructure services provider who share infrastructure with other customers through the Internet. With public cloud, you’ll buy the cloud services and your team will take responsibility for implementing business application and networking from the cloud to your customers.
A private cloud could be on-premises or off, but you are the only tenant on the infrastructure. This is like traditional I.T. and typically adds overarching deployment and management tools to rapidly delivery new I.T. services or management changes. Your team will be responsible for architecting the infrastructure, implementing the hardware and software and supporting it.
Software-as-a-service is where a provider offers specific applications running on their I.T. infrastructure and delivered via the Internet. A common example of this is salesforce.com. In this case, you’ll purchase the services and your team will provide value-add with services like implementation, training, customization, security policies, etc.
A hybrid cloud will probably become the most common deployment. This is some combination of public cloud, private cloud, and software-as-a-service. Your team will deliver customization, integration, management, training, for a complete business I.T. system.