Apologies to The Rolling Stones, but these days we’re talking about software—software delivered over the internet by providers such as xRM.
What’s the Cloud?
The cloud is that nebulous virtual software space out there where software resides when it doesn’t reside on your computer. That virtual space is made possible by very real hardware, but the twist is that end-users don’t need to own, or even know about, the hardware. The hardware is operated by hosting companies.
Server virtualization also allows the software to move from one real hardware location to another, transparently to the end-user. Virtualization allows hosting providers to be greener — turning off some hardware and saving electricity during low-demand periods, without interrupting service.
What’s the public cloud?
The public cloud is what most of us use every day. The public cloud provides software that is accessible to anyone with an internet connection. When you go to any popular search engine or free email site, you use software running on a machine somewhere else to get work done. A portion of the software is presented to you in your browser for you to interact with, but most of it runs elsewhere.
What’s a private cloud?
A private cloud is a segregated, secure, software-hosting space that is not publically accessible. It can only be accessed by that group of people authorized to do so. A private cloud enables a business or other organization to take advantage of having its software in the cloud (thus offloading the hardware- and software-maintenance tasks to the hosting provider), while retaining the privacy that is critical to daily operations.
If required, private clouds can also be restricted to particular hardware locations in what is called a “dedicated environment”. That means that the software and related data are not moved by server virtualization when adjusting to service load. It also means that the hardware location is dedicated to one business, ensuring complete hardware isolation as well as software isolation. Some businesses and governmental organizations are mandated by law to hold their data on dedicated hardware. A dedicated hosted environment allows even those groups to take advantage of the cloud without losing the hardware isolation they must have.
Thanks to: http://blog.xrm.com/index.php/2013/09/get-off-of-my-cloud-its-private/