Most enterprises that have private clouds use some type of method, such as chargeback or physical limits on the amount of capacity that users can request, to keep the lid on demand. Otherwise, users might just keep provisioning virtual servers and use up the capacity quickly.
Essential cloud components
Jeffrey Driscoll, a systems engineer at consultancy Precision IT, advises that when companies start building a private cloud, the basic building blocks are servers, storage such as a SAN, and virtualization software. "Then you start building a cluster," he says, and after that cluster is complete, "capacity planning becomes critical."
Capacity planning involves figuring out what happens when you add servers and other resources to the cluster as needed to keep up with business demand. Capacity planning is a major component of the cluster and the cloud's performance. If it's done wrong, you might end up with useless systems or have to shoehorn in traditional, non-cloud systems to keep things running.
What do you see as the drawbacks of private clouds compared to public clouds?
(Check all that apply.)
Having to build it all internally: time, cost, learning curve for IT: 50%
Having to implement virtualization, automation and orchestration when we didn't have those tools before: 30%
No drawbacks: 11%
Source: Computerworld online survey; 54 respondents
Most organizations are not good at monitoring and keeping ahead of capacity. To be able to satisfy user demands, you always have to have some extra capacity on the data center floor, which means a certain amount of hardware sitting around in idle mode. Keeping a history of capacity usage in your enterprise can help you make sure that you have sufficient -- but not too much -- capacity.
One solution is to create a hybrid cloud environment and, when capacity is not available in the private cloud, move requests for capacity to public clouds such as Amazon Elastic Compute Cloud.
Once the cluster is up and running, you can start provisioning virtual servers. The result is a tiered architecture with a server layer, a network layer and a virtualization layer. There is a management tool at each layer. "Now you can start thinking about automation," Driscoll says.
Some security concerns
Driscoll says that private clouds are great for businesses with security concerns or regulatory requirements, although Suncorp's Cameron says that private clouds force implementers to rethink how they do security.
Are you implementing chargeback or some kind of pay-per-use model for your end-users to pay for their piece of the private cloud?
No, we had chargeback/pay per use before the cloud: 18%