Xen Hypervisor 4.4 Released

Xen 4.4 was released on the 10th of March.  Here is a very brief summary of the enhancement achieved in this release.

The ARM port has reached an improved level of stability.  Hypervisor ABI (Application Binary Interface) has been "declared stable" (according to the release notes).  AMD have demonstrated an ARM based Opteron (A1100 Series) recently.  I think this represents the start of a huge potential change to cloud compute engines.  It's early days yet but with this release this future reality moves a lot closer.

 Intel Nested Virtualisation has been declared 'Tech Preview'.  This means that stability, reliability and performance have been greatly improved, allowing for nested KVM, Xen, VMWare and MS Hyper-V to run on top of Xen.  More info.  This is currently not recommended for production but does mean that lab based replicas of a production cloud could now more reliably run on top of the Xen Hypervisor.

The Xen Project blog post about the release lists as "probably the most important" hypervisor improvements to "libvirt support for libxl" .  Libvirt is a 'virtualisation API' that supports a multitude of hypervisor and container systems.  Libxl is a small lower-level C API library created so that Xen Toolstacks could share a common API set instead of writing their own libraries for common Xen operations.  More info here.  The enhancements made should make it easier to integrate Xen into cloud orchestration engines such as Cloudstack as it would allow a common toolstack (libvirt) to be used when talking to different hypervisors.  

Note: according to the Xen Wiki, work is underway to port the XAPI API to use libxl (libxenlight).

Note: XenServer 6.2 incorporates the Xen Project hypervisor 4.1.5.  It will take some time for the new hypervisor to be integrated into the Citrix release, as it will for other commercially supported versions.

More information can be found at Xen Project 4.4 Release Notes.