“Cloud Computing” – it means different things to different people. To help clarify things, I’ve come up with a “cloud continuum” that better describes the different offerings that are out there.
As you can see I’ve used the common terms of SaaS (Software as a Service), PaaS (Platform as a Service) and IaaS (Infrastructure as a Service) as the primary demarcations. But the key point is that it really is a continuum – many offerings blur the boundaries to the point where rigid definitions of the above terms don’t really help anyone.
For example, Salesforce.com is held up as the classic example of SaaS – sign up for the service and you have a full featured CRM available to you immediately. Configuration and customisation can all be done via your web browser. “Great – it fits in the SaaS box” you say…but not quite…
Force.com is the platform under-pinning Salesforce.com – and on Force.com you can build any type of application you like – CRM related or not. We use the Force.com platform quite a bit when addressing our customers’ custom requirements for their Salesforce deployments – and so we end up with a hybrid solution that leverages the best of the SaaS CRM with the PaaS features of Force.com.
Thus a typical Salesforce.com implementation for a complex client spans the SaaS and PaaS aspects of the continuum.
Google AppEngine and Windows Azure are essentially straight PaaS solutions – take your application component and deploy into the platform. However, Azure pushes into the IaaS aspects of cloud computing – for example, by offering relatively low level SQL Server features in a way not dissimilar to what you essentially get when starting an “off the shelf” Windows SQL Server AMI on Amazon EC2.
Amazon EC2 is predominantly IaaS; and apart from some specific limitations, mainly around networking, is not too dissimilar from that of mass-market virtualisation providers or what large enterprise IT teams offer their internal customers in “private clouds”.
Overall, my idea of putting forward a continuum for cloud computing is to avoid us getting hung up on specific definitions or labels for each area. It also reflects the fact that in the world of cloud computing providers can quickly add new features that expand their presence across the continuum.
Clearly we are going to see massive growth in all aspects of the continuum over the coming years – but I envision the biggest and most influential changes will be in the area of platform as a service. Google and Microsoft are making major moves here that will transform the way we deliver IT solutions.
