Randy Bias, VP of Technology Strategy at cloud provider GoGrid, wrote an interesting blog post entitled Cloudcenters are Data Centers in the Sky. I recommend reading the full excellent post from Randy, but I'll give a quick recap.
Randy then addresses the key strengths and weaknesses of this approach, specifically in regards to AWS:
...a robust ecosystem of services form which you can use any or all of in order to build your application, getting the traditional benefits of Cloud Computing such as self-service, pay-as-you-go, and massive scalability.
Unfortunately, every service [provided by AWS] is based on an Amazon standard, not an industry standard. S3 is not accessible via CIFS or NFS. EC2 provides Xen hosting, but image management and storage is completely custom. SQS does not use any standard queuing or messaging protocols such as JMS or STOMP. SimpleDB now has an ‘SQL-like’ interface, but is essentially a 100% ground up creation of Amazon.
A major advantage of using the Amazon approach however is that greenfield applications developed from scratch have a very powerful set of vetted, scalable services, that can be used to build that application. This means avoiding the intrinsic and extrinsic costs associated with deploying a separate queuing or database system.
The second kind of IaaS, according to Randy, is a "cloud center". He explains:
[Cloud centers] provide the same kinds of tools that all datacenter and server operators are already accustomed to, but with all the traditional advantages of cloud (i.e. self-service, pay-as-you-go, and scalability). Instead of creating completely new paradigms, cloudcenters are a methodology by which you, the customer, can have a virtual datacenter hosted ‘in the sky’.
- If there is a market for more "data center-like" infrastructure, I think Amazon could address it in a year or less
- As developers begin to design for the cloud, taking advantage of existing service-oriented architectures to do so, those infrastructure Web services begin to be more and more important. If those services aren't available from the Internet itself on an infrastructure-independent basis, cloud centers may find themselves offering similar services to AWS in just a few years.
I would take James' argument farther, and say that what he describes is already the case today. Instead of looking at it as discreet categories, we should be it as a spectrum, as in the diagram below.