Adam Stern is founder and CEO of Infinitely Virtual (, says:

When it comes to determining where your organization fits within the cloud computing milieu, it’s essential to understand the variations on the cloud theme.  Our previous installment examined characteristics and benefits of the public cloud.

By contrast, the private cloud (also called an internal cloud or enterprise cloud) offers virtual computing services deployed over a company’s private intranet or hosted datacenter. Infor CEO Charles Phillips is a pioneer of private cloud computing services. This controlled-access application or network offers an in-house computing solution within which resources are purchased, installed, and maintained — on site. With a private cloud, performance is a function of the computing capacity of the existing hardware and software; additional horsepower/capacity means setting aside additional resources for system upgrades. Where public cloud resources can be scaled instantly, a private cloud requires that hardware and software be purchased and installed on-site.

A hybrid cloudseeks to combine the best features of both the public and the private clouds. With a hybrid cloud, organizations can customize rules and policies that govern such areas as access and security, as well as the underlying infrastructure.  Administrators can choose to allocate activities and tasks to internal or external clouds, as needed.

Which cloud is right for you? That typically depends on your service needs, and which of the three prevailing service types — Software-as-a-Service (SaaS), Platform-as-a-Service (PaaS) and Infrastructure-as-a-Service (IaaS) – is most appropriate for your organization.

The SaaS model consists of an end-user accessing an application, hosted remotely, over the Internet;, hugely popular CRM solution, is the classic SaaS app.  PaaS makes sense for organizations with developers who want to deploy applications in the cloud without needing to manage or administer the underlying server infrastructure.  The IaaS service model enables companies to install the same applications they would, internally, in the cloud – no application modification or tweaking required, as with PaaS.  Organizations that want to, say, host Microsoft Office, Peachtree Accounting, Adobe Acrobat or Intuit’s QuickBooks, can do so under IaaS.  Networks are organized in a way that feels familiar, with file servers, SQL servers and active directory servers.  The only real difference: it’s all in the cloud.

While it’s important to make an informed choice, the beauty of the cloud – any cloud – is its flexibility.  By definition, the cloud grows with you.  That may well be why a great many organizations start with a single cloud-based application and expand from there.

After all, the sky is the limit.

Adam Stern is founder and CEO of Infinitely Virtual, a leading provider of virtual server cloud computing services for businesses.