You may also have to re-architect deployment of legacy applications to take advantage of private clouds. Many legacy applications are running on mainframes and proprietary Unix platforms. Most virtualized environments, including private clouds, are geared to run on x86-based systems.
Also, in a virtualized environment, we generally don't know exactly where an application is running at any given time. Because most legacy applications are tied to a specific platform, running them in a private cloud will often require re-architecting them.
Divorcing applications from the hardware is a hallmark of clouds, including private clouds. In a traditional data center, those 10 servers over there might be running billing applications and those five over there running CRM apps. With a private cloud, however, it's not known ahead of time which servers are running which specific applications. The applications run on whichever servers have free cycles at the time the apps need to run.
Private clouds involve two groups: the IT (data center) operations folks and the business users who want to run applications. A private cloud gives business users the opportunity to quickly provision a server and run an application when they want to -- without human intervention.
The IT operations folks have to make sure that sufficient resources are available for the type of on-demand computing that business users have heard is available with public clouds, and that usually means that the wait for user-requested resources is minutes, not days. Anything short of this, and users will be unhappy.
This is what private clouds are all about: providing the on-demand elasticity of public clouds but doing it within the company's firewall.
Another difference is that some IT managers or business users may expect private clouds to act like public clouds. In a public cloud, the public cloud provider's IT operations group is responsible for the compute infrastructure, and the enterprise's business application groups manage and monitor their own applications, under agreement, on the public cloud. If the private cloud is expected to operate in a similar manner, that means the IT group may need to give up its traditional application-management role.
The steps for transition
The first thing is to broaden out beyond server virtualization. At this point, a lot of users are looking at virtualization for purposes of availability. So look at those aspects of virtual infrastructure that improve availability as the next steps toward a private cloud.