It won’t take long when you start investigating Cloud Computing, for you to come up against several common acronyms. You’ve probably already seen the “AAS” endings already, but these “As A Service” offerings make up the core of the major vendors’ assault on the Cloud. The three we will cover in this article are SAAS,IAAS and PAAS.
What is SAAS?
The venerable old-guard of the Cloud is Software as a Service. Strangely, given its position in the application layer of any solution, you might expect this to be one of the last kinds of solution to become available due to its reliance on other parts of the computing infrastructure.
In reality, many application vendors pushed ahead, either converting existing monolithic solutions, or writing all of the needed infrastructure code themselves to make it possible to run their software package across the internet.
By and large, SAAS packages are written to offer what is known as multi-tenancy. Conceptually this means that a single large instance of the package can support many customers with all necessary safeguards in place to ensure that they never interact with each other (and effectively believe they have the machine to themselves).
This large instance may actually be run across many physical machines, or may be virtualized in such a way that a new virtual machine is run for each customer, giving better separation, but more administration headaches for the vendor.
The economies of scale made possible by this approach and the lower per-user costs that arise are among the strongest reasons for the success of the SAAS model. The downside of such an approach is that all business data associated with the application is completely outside the control of the business using the service.
Example vendor in this space: Salesforce
What is IAAS?
Infrastructure as a service deals with the fundamental building blocks of the IT universe; the processor and storage needs of any application.
With the rise of cheap virtualization solutions, with support built into many modern CPU architectures, it has become much easier to segment or combine the processing power of multiple chips into exactly the right amount of compute capacity.
Not only that, but the dynamic nature of recent virtualization solutions makes it just as easy to add or subtract power when needed as it is to make that initial segmentation.
Network-accessible storage has been available for so long that it is even making its way into domestic usage and so is an obvious addition into a cloud based storage service.
In fact, in many ways, a storage service is a much more easily quantified service offering for a vendor. Storage space used is much easier to measure (at this current time) than just exactly how much of any virtualized chip you have used. Look for this to be an area of extra work in the IAAS space.
Example vendor in this space: Amazon Web Service (Amazon EC2)
What is PAAS?
Platform as a Service is phrase you are more likely to hear if you are dealing with the major computing infrastructure players and springs from all of their earlier works in building service oriented architecture offerings.
While my own experience in this space springs from my work at BEA (before the Oracle acquisition), it is certainly helpful to be able to think of any application as being delivered by a series of layers.
The infrastructure layer in the cloud has been dealt with above, but there is a clearly defined need for a layer that handles all of the heavy-lifting needed to build a reliable, secure, scalable application.
In the heyday of the “application server” we described this as “the software beneath the waterline” on an imaginary iceberg and that analogy is still valid today.
If your business relies on you creating new, highly-targeted applications for your customer base (rather than trying to retro-fit a more generic SAAS solution) then you may be in need of a more “platform” oriented approach.
You should be able to rely on your PAAS vendor to get all of the necessary pieces in place to allow you to build your own cloud application without having to concern yourself with things like the requirements I mentioned above. Not only that, but you also need the PAAS solution to extend further into things like handling multi-tenancy for you and also resource usage measurement – how else will you know how much to charge your customers.
The beauty of the PAAS concept is that it encompasses all of these requirements, throwing in common interfaces to rich clients at the front end and to databases and storage at the back end while keeping all the complexity of that hidden from your business application developers.
We saw a move in the 90’s and 00’s towards application vendors using application servers as their platform of choice for new versions of their software (removing at a stroke the need to support all of that internal “management” functionality). We should fully expect more and more Cloud offerings to also move towards relying on PAAS solutions in the same way. This in turn will allow smaller companies to bring Cloud services to the market that focus on just providing business value without the need to develop the rest of the infrastructure handling.
Example vendor in this space: Oracle