Cloud Computing – A Taxonomy

Cloud computing is becoming important for very massive messaging systems, such as Gmail and Microsoft Exchange Online. And there is no doubt that "cloud computing" is the IT industry's latest "buzz" phrase, but what does it mean?

At its simplest, it describes computing cycles delivered over the net. But how is this different from the 1960s time-sharing or today's access to on-premise server-based applications? At one level it isn't, but at another it is, because today's "cloud" refers to the public Internet. So "cloud computing" refers to computing cycles delivered over the public Internet. This form of "cloud computing" can be delivered in three guises:

  • As Public Services (PSs) hosted in large, multisite data centers and delivered over the public Internet -- for example, Google Search, Google Apps, Facebook, etc.
  • As Virtual Private Services (VPSs) hosted in large, multisite, multitenanted data centers and delivered securely over the public Internet -- for example, Microsoft Exchange Online, Salesforce.com, etc. These VPSs are sometimes referred to as Software as a Service (SaaS).
  • As Private Applications (PAs) hosted in large, multisite, multitenanted data centers and delivered securely over the public Internet. These are end-user applications that are currently hosted on-premise, and which in future will run in the cloud.

Note that PAs can easily morph into VPSs, and VPSs can morph into PSs. This is because all three can employ the same platform. It is more difficult to morph in the opposite direction. For example, turning a PS into a VPS may take a considerable amount of work, such as operating with multiple unfederated directories. Similarly, a platform for hosting a PS may or may not be appropriate for hosting a PA.

PAs explicitly, and PSs and VPSs implicitly, require a platform in the same way that traditional on-premise applications have required a platform. Historically, these on-premise platforms have been operating systems (OSs). More recently, these on-premise platforms have been elevated a level. Examples include .NET, J2EE, J2ME, etc.

So what form might a PA platform take? There are currently a number of candidates. These include:

  • Amazon's EC2
  • IBM's Blue Cloud
  • Microsoft's Windows Azure

We will address these three in future postings.

... Nick Shelness

One Comment

  1. Posted December 20, 2008 at 3:02 PM | Permalink

    Hi, Nick!

    You’re absolutely on point with those PA’s requiring a platform on an elevated level. Call them the ‘cloud’ tenants which signal a boom in web apps delivered not just to your PC but to mobile as well.

    Happy Holidays!

    Best.
    Alain Yap
    Morph Labs

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