Rackspace has years of experience with running Xen at scale, starting with Xen and migrating to XenServer. We will share why we use Xen/XenServer along with some of the issues that we've experienced. We will touch on our experience with migrating from Xen to XenServer and the challenges there. We will share information about Rackspace Cloud Servers architecture, and touch briefly on OpenStack when doing so. We will explain how we use Xen to quickly deploy new Openstack services with what we call Nova on Nova. And finally, we will discuss what additional features and improvements are needed and why.