Obviously vCloud Director uses the vCenter API. This means a user of vCloud Director has access to the full functionality implemented in vSphere.

Conclusion: This is a commercial product and that is a big disadvantage for some users. However, if you already use VMware for virtualization, vCloud Director will be the most appropriate choice.

is an open-source platform for deploying clouds. This project includes three products: Nova (an analog to Amazon EC2), Swift (an analog to Amazon S3), and Glance (an API server that provides discovery, registration, and delivery services for virtual disk images). In our research, we only used Nova, but you should pay close attention to Swift, which offers scalable object storage for petabytes of accessible data. OpenStack 2011.3 is supported by many vendors, including CloudStack 3.

Currently, Nova fully supports two hypervisors: KVM and XEN. The platform is being developed rapidly and soon will be provided with a broader functionality. The technology is popular among a large community of specialists and is backed by such companies as , Dell, NASA, Intel, AMD, Citrix, Rackspace, and RightScale. The core of this product is developed by NASA.