Citrix XenServer is a server virtualization platform based on the Xen hypervisor that allows IT administrators to host, deploy and manage virtual machines.
The main components of Citrix XenServer are the hypervisor, XenCenter integrated management and XenMotion live migration. The platform also delivers free tools for physical-to-virtual and virtual-to-virtual server conversion. It supports up to 500 virtual machines (VMs) and 4,000 virtual CPUs per host. XenServer is designed to work specifically with Citrix Systems’ XenApp and XenDesktop tools for desktop and application virtualization.
Prior to XenServer 6.2, IT administrators could download only the base hypervisor for free and deploy as many VMs as they wanted, but the hypervisor lacked many key features such as storage integration and strong load balancing. Version 6.5 extended some of the capabilities from the Enterprise and Platinum editions to the basic edition, but that version is no longer completely free. IT shops have to pay licensing and support fees, which includes 24/7 service, Subscription Advantage upgrade rights and XenCenter automatic updates. Support is not unlimited, however; it is on a per-incident basis.
The latest edition of XenServer features 64-bit architecture that allows it to deliver faster, more efficient VMs than past versions. In addition, it emphasizes scalability and density for VM farms.