Well, I wish I could answer that question, but in an attempt to help wrap my head around this latest paradigm, I'll try to organize my thoughts around some of the concepts of cloud computing.
When talking about cloud computing, there are a couple of types of clouds that come up, mainly
- private clouds
- public clouds
Regardless of whether or not it is public or private, the bigger question is "What the heck is a cloud?". Well, like a lot of new technology buzzwords or concepts, the answer is often "It depends". In this case, there seem to be many different "levels" for computing within a cloud. One good way of classifying the cloud computing options is to look at the level of the stack that they are servicing. With this approach, there appear to be a few different options for providing solutions from the cloud:
- IAAS (Infrastructure As A Service)
- PAAS (Platform As A Service)
- SAAS (Software As A Service)
- DAAS (Desktop As A Service)
This seems to be the cloud offering that is at the lowest level of the stack. It is generally a computing infrastructure that is provided to the client (essentially at the operating system level). This is somewhat analogous to "virtualization", where a single physical machines can be partitioned and then treated as multiple logical machines (just on a different scale, with many physical machines serving as many more logical machines). However, it can sometimes be the inverse, with many physical machines looking like a single logical machine (more of a clustering approach). All of this is somewhat transparent to the individual logical machines.
PAAS
The Platform As A Service approach takes it up another level, generally providing some sort of software or application stack as part of the service (like a Java Application Server with a Database implementation, or a LAMP stack, or some other similar offering). This offering is generally considered as a deployment infrastructure for an application that can shrink and grow with user demand for that application.
SAAS
This approach takes it up yet another level, generally offering some sort of application as a service from the cloud. The classic example for this type of cloud offering is Salesforce.com (SFDC). Where it comes a bit more challenging in my mind is how to separate this from normal web applications. What is different in an SAAS offering that makes is "cloud"? Or is it just a fancy way of saying web application? For example, would you consider most online email offerings as "cloud" applications (or SAAS)? If that's the case, you can probably roll in Google Apps, as well as other web-based application services (including the software used to run this blog).
DAAS
The Desktop As A Service is a relatively newer term (at least to me), but the concept has been around for some time. It is roughly analagous to the desktop virtualization and conceptually similar to the platform virtualization discussed above. It seems to be a fancy method of referring to some of the remote access and remote control technologies used in the past, and not really indicative of the cloud computing movement that most enterprise vendors are pushing (near as I can tell).
In fact, referring to DAAS as a "cloud" technology doesn't quite make sense to me, but this seems to be at least part of Microsoft's vision for the cloud (based on the commercial that I mentioned in the beginning of this post, where there are a couple of people stuck at an airport, and appear to connect to their home PC over the web and look at photos or watch some recorded TV shows).
As you can see, there are many differing visions for this "cloud" future (depending on which vendor you ask), and I'm still not quite sure which one I buy into. In reality, I suspect there is a place for several, if not all, of these versions of the cloud. Like all other technology solutions, the correct choice will likely depend on the business problem that you are trying to solve...
