The Cloud Computing movement is a melting pot of distributed technologies and paradigms that produce new terms at an incredible fast pace. So it is usually difficult for newcomers to figure out how to take advantage of these new technologies or if they fit in their current IT infrastructure at all.

So, let us try to classify the current infrastructure provisioning trends (the IaaS brand of Cloud Computing) using two simple parameters: where do you obtain the resources for your applications (locally or remotely), and how are those resources obtained (physical or virtualized):

• Own site (Local – Physical): This is the classical provisioning scheme that we’ve been using for years, one service one machine; not much to say here.
• Grid (Remote – Physical): the resources are obtained from a remote site for an specific service, eg. batch job processing in scientific Grids, or web applications in a typical hosting scenario. In this case you get fixed configurations with a limited control over the remote resources
• Private Cloud (Local – Virtual): the resources are obtained from your own infrastructure in the form of Virtual Machines. So you can obtained the classical benefits of virtualization (e.g. consolidation, isolation, easy replication of configurations…) but for your infrastructure as a whole and not just for one server.
• The Cloud (Remote – Virtual): the resources are obtained from an external (cloud) provider. Unlike the Grid and thanks to VMs, you have total control of the resources you are “buying”, you can install what you need. Usually the provider in this case is another company, but it could be a partner, in that case it is called a Community Cloud.

Let’s briefly review three resource provisioning examples in use:

Classical IT Outsourcing (Own site + Grid). This is the well accepted provisioning scheme adopted by many companies. Some of the core services are hosted in the in-house infrastructure and others are moved to an external hosting. Usually research centers use this model to store and analyze big amounts of data, such as those generated by LHC, or to solve grand challenge applications

Cloud Outsourcing (Own site + Cloud). Similar as above but you get VM’s instead of pre-configured environments to support your service workload. In this case, the VMs can be configured to register to the local services(e.g. a clustered web server), so the capacity assigned to the service can grow with its demands.

The Hybrid Cloud (Private Cloud + Cloud). Nowadays the use of Virtual Machines is a common practice, for example to easily get developing and testing environments. This model can be combined with a Cloud if the some of VMs are obtained from a remote provider, typically to satisfy peak demands.

Probably, using this quadrant you can better plan the resource provision strategy for your site or understand what they are trying to sell to you!

Ruben S. Montero