At the bottom sits the resource tier comprising infrastructure, platforms or software. Raw virtualization comes to mind immediately, but VMs aren't the only option – as long as you've got a mechanism for turning resources into a pool you're on the way, Bittman says. Rapid re-provisioning technology is another option, for example.
Above the resource pool sits the resource management tier. "This is where I manage that pool in an automated manner," says Bittman, noting that for VMware environments, this is about using VMware Distributed Resource Scheduler.
"These two levels are fairly mature," Bittman says. "You can find products for these available in the market, although there's not a lot of competition yet at the resource management tier."
Next comes the service management tier. "This is where there's more magic required," he says. "I need something that lets me do service governance, something that lets me convert pools of resources into service levels. In the end, I need to be able to present to the user some kind of service-level interface that says 'performance' or 'availability' and have this services management tier for delivering on that."
As you think about building your private cloud, understand that the gap between need and product availability is pretty big, Bittman says. "VMware, for example, does a really good job of allowing you to manage your virtualization pool, but it doesn't know anything about services. VMware's vCenter AppSpeed is one early attempt to get started on this," he adds.
"What we really need is a good service governor, and that doesn't exist yet," says Bittman.
Sitting atop it all is the access management tier, which is all about the user self-service interface. "It presents a service catalog, and gives users all the knobs to turn and lets you manage subscribers,” Bittman says. "The interface has to be tied in some way to costing and chargeback, or at least metering – it ties to the service management tier at that level."
Chargeback is a particularly thorny challenge for private cloud builders, but one that they can't ignore for long. "It's tricky from a technology perspective -- what do I charge based on? But also from political and cultural perspectives," Bittman says. "But frankly, if I'm going to move to cloud computing I'm going to move to a chargeback model so that's going to be one of the barriers that needs to be broken anyways."
In the end, it's about the business