CloudStack vs OnApp

CloudStack is open source software written in java that is designed to deploy and manage large networks of virtual machines, as a highly available, scalable cloud computing platform. CloudStack current supports the most popular hypervisors VMware, Oracle VM, KVM, XenServer and Xen Cloud Platform. CloudStack offers three ways to manage cloud computing environments: a easy-to-use web interface, command line and a full-featured RESTful API.
OnApp software enables Infrastructure-as-a-Service for hosts, telcos and other service providers. With OnApp in your datacenter you can use commodity hardware to sell public & private cloud services, dedicated servers, Virtual Private Servers, CDN, DNS, storage and much more, through one fully automated control panel.
Face to face in the news:

2011 - Citrix acquired cloud platform to defeate OnApp


Virtualization and Cloud Computing: these technologies have become very linked in the recent years. And the virtualization market leaders want to become the leading providers of cloud platforms. Microsoft created Windows Azure, VMWare - vCloud and recently Cloud Foundry. Citrix is the last of the three virtualization giants to fly into the Cloud. Until now, the company only supplied software for private clouds, but didn't provide its own cloud infrastructure. Today, Citrix (for the amount between $200 and $250 million) has acquired the cloud provider It's a pretty successful platform with big client names: Zynga, Tata, GoDaddy. uses the open-source platform OpenStack as the cloud operating system. It was created by the alliance led by RackSpace. Citrix also participate in this alliance, and after buying, is going to continue support OpenStack and integrate it with own virtualization technologies.