There is a continuous debate surrounding THE definition of cloud computing.
Is it just another name for Virtualization? Is it a “re-packaging” of Grid Computing? Or is it just the familiar hosting services we know and love with an additional (and more sophisticated) layer of automation?
To be honest – I think it will be very hard to finalize this debate conclusively by just sticking to high-level terminologies. As technical folks we often tend to dive into technical debates and in the course of doing so, we loose sight of the reasons that brought up this debate in the first place. The discussion about the definition of cloud computing is no exception.
Instead of continuing the endless debate, I thought that taking an end-user view would be much simpler to agree on. Here is a snippet from a response that I gave on one of the recent threads on the cloud mailing list: Is “Internal Cloud” an oxymoron? that tries to address this question:
1. On demand computing i.e. the ability to get a resource when I need it in matters of minutes.
2. Pay-per use i.e. the ability to pay only for what I use.
In my view what we will see in the near future is a hybrid-cloud i.e. local-IT + Internet Cloud. A typical scenario would be to run testing on public cloud and production internally. There are many other scenarios that justify this type of hybrid model.
This thinking was later enhanced by Miha Ahronovitz in his response on another thread here.
Understanding the cloud-stack by analogy
Another way that I found useful when I need to explain the cloud-stack is by analogy to the existing application stack:
The above diagram is a very simplified view of the world. It explains (without too many words) the analogy between today’s world, which consists of dedicated resources per application, to the cloud world, which consists of a virtualized pool of resources. As can be seen in this diagram, Applications morphs into Software-as-a-Service, Middleware morphs into Platform-as-a-Service and Operating-System, Hardware and Network morphs into Infrastructure-as-a-Service.
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