I’m a big fan of metaphors to help describe new technologies since they often help people that aren’t immersed in the stuff on a daily basis gain a quick understanding by building a crosswalk to those things with which they are familiar. Of course I fully appreciate the limitations of metaphors as well. I can’t tell you how many debates that have been started as the trolls look for any discontinuities in the examples used.
It’s been interesting to be caught up in the technology transformation that we know as cloud computing. While this transformation has had a significant impact on how technology is delivered, it also has had a significant impact on people having the conversation on these technologies. No longer are only the technology people discussing new ways of delivering the services, it’s also the organization’s service delivery leaders, the financial group, the legal group and even the board of directors level that are actively engaged in the conversation. This is where the challenge arises. Cloud is an umbrella term that covers a wide variety of technologies, processes and even philosophies for delivering IT as a service. All these different permutations and combinations can quickly lead to confusion and rat-holing when decisions need to be made. Enter the metaphor.
One of my favourite places to look for a metaphor is the automotive industry, and I’ve used the collection of parts, kit car and dealership example to try to characterize cloud services. I’ve also used the lumberyard, pre-manufactured home and site built homes as well. Unfortunately, I still get some blank stares from the audience (maybe it’s just my delivery 
). So I gave it a little more thought and came up with what I think is an example that I think everyone can relate to and doesn’t give the trolls too much to complain about. Since everyone needs a place to live, I thought that the housing example, refocused, could serve as a useful way to help clarify the different cloud services. Here it goes:
When organizations are looking to gain an appreciation of the degree of flexibility offered by the cloud service delivery models of Public, Community/Hosted and Private cloud, confusion often arises within the various stakeholders. A simplified approach may be to use the metaphor of apartment, condominium and building ownership to help illustrate the respective levels of specialization an organization can expect.
Public Cloud as an Apartment
If you think back to when you rented an apartment, you’ll remember in addition to looking for a space that fits all your stuff you also considered what services were included in the monthly rent. Electricity, Water, Gas, Heat and even cable came up in the discussion. Even paint colours (configurations of the space) could be limited (no flat black walls please). Ultimately, it was all described in the standard rental agreement which was the same for all tenants. Public cloud services are not unlike the apartment model in that they provide a given set of packaged services to a broad community. If you find a cloud offering that you think fits, you complete legal agreements and set off to configure them to meet your needs. Just like you aren’t able to tear out a wall or encroach on your neighbor in the rental, the public cloud offering will also note the extent of customization possible. Finally, like the apartment where you rely on city inspectors for their review of the building, public cloud services will have third party reviews to provide subscribers with assurance.
Community Cloud as a Condominium
For many people, a condominium provides them with additional say in their living space, albeit with an additional cost if the form of condominium fees. The condominium can provide the resident with the ability to configure their internal space as they see fit. Replacing fixtures, changing floors and other light customizations are generally permitted. Since many condos also share common space, a community association is typically established to define those common services the community can use. In some cases, there may also be agreement on common standards to adhere to for community (exterior colours, roofing, public spaces). Community clouds have similarities in that they provide customer clusters with the ability to customize services across the community. Through the community, each tenant has a voice in what services are generally provided as well as the manner in which the service can be used. Like a condominium where significant infrastructure upgrades (say, window replacement) can be scheduled based upon the residents, often community cloud services provide the ability to define the timing of significant changes. Finally, the condo agreement often provides tenants the flexibility for input and adjustments to meet their requirements.
Private Cloud and the Building Owner
Sometimes it’s a noisy neighbour, sometimes it’s the ability to put that new satellite dish on the roof but there may come a time where you want to have full control over your entire domain. In those cases you need to buy the building. When you own and manage the building, you have full reign to customize the spaces, but will find that you also have full accountability for them as well. Of course, this generally comes with added expense as well. As a building owner you can often save money by adopting the practices of others, be they preventative maintenance to environmental sustainability. There is a similarity here with Private cloud where organizations operate the infrastructure they own. Adopting private cloud processes and philosophies will allow organizations to gain some of the efficiencies found in the other cloud models while continuing to be in full control of all aspects of the service.
So while all metaphors have their pitfalls (I haven’t figured out yet how to make the above mentioned spaces elastic so that they expand when more capacity is needed 
), I think you’ll find these helpful in framing the degree of specialization each cloud model accommodates.
