XenServer 6.5 is available in Standard Edition and Enterprise Edition
On 13th January 2015 Citrix released XenServer 6.5, offering a 64bit Dom0 and significant networking and disk performance increase.
In May 2015, XenServer 6.5.0 Service Pack 1 came with new features, see http://support.citrix.com/article/CTX142355
-Enhanced guest support
-Intel GVT-d Pass-through support for Windows VMs
-NVIDIA GPU Pass-through support for Linux VMs
-Ability to manage and monitor Docker™ containers using XenCenter
-Improved user experience for read caching. Customers can now see the status of read caching in XenCenter
Citrix announced in April 2013 that XenServer will be made available open source, as a Linux Foundation Collaborative Project, see http://xenserver.org/.
What is the difference between XenServer and the open-source Xen Project Hypervisor?
The Xen Project hypervisor is used by XenServer. In addition to the open-source Xen Project hypervisor, Citrix XenServer includes:
Control domain (dom0)
XenCenter - A Windows client for VM management
VM Templates for installing popular operating systems as VMs
Enterprise level support
Citrix entered the Hypervisor market with the acquisition of XenSource - the main supporter of the open source Xen project - in Oct 2007. The Xen project continues to exist, see http://www.xen.org/.
Citrix created a suite of commercial products that are named after the open source project including XenApp (aka Presentation Server), XenDesktop (Citrixs hosted virtual desktop/VDI solution) and XenServer (the only product actually based on the open source Xen hypervisor code.
XenServer uses paravirtualization and hardware-assisted virtualization, requiring either a modified guest OSs or hardware assisted CPUs (more commonly seen as its less restrictive and hardware assisted CPUs like Intel VT/AMD-V have become standard). The device drivers are provided through a Linux-based guest (CentOS) running in a control virtual machine (Dom0).