The data center may seem like old news, but advances in virtualization, cloud computing and management technologies continue to challenge and aid administrators. Our first classroom focuses on how maturing cloud services can help enterprises save money and maintain reliable disaster recovery. The second classroom reviews the criteria for selecting data center hardware, including energy efficiency, design tradeoffs between blade and rack servers, and server deployment and migration. The third classroom looks at how to build a mixed infrastructure. It discusses how to assess whether you need a second hypervisor, how to add a new hypervisor to a virtual infrastructure and how third-party tools can help manage mixed virtual environments.