Why Use Xen?


At the Linux Foundation Collaboration Summit in April, the Xen Project announced that it was now a Collaborative Project of the Linux Foundation.  But as people attended some of the Xen-related conference sessions, one question always seemed to be asked: “Why should I use Xen?”

There is an answer – but it varies depending on the audience.

Xen logo and pandaFor the business person, the answer is that Xen is a safe, stable, well-tested choice for virtualization which is used by industry giants (Amazon, Rackspace, Verizon, etc.).  It has a robust consortium of companies behind its development and it has the price, performance, and security to go toe-to-toe with the best offerings in the industry.  Plus, it has a proven 10-year track record which includes powering some of the largest clouds in the world.

For tech-savvy users of F/OSS, however, there are additional considerations.  A few of these include:

·         Type 1 Hypervisor: The fact that the Xen Project employs a Type 1 Hypervisor – a hypervisor that runs on bare metal rather than within an existing operating system kernel. This means its architecture has special attributes when it comes to scale, security, and performance.

·         Disaggregation: The ability to segment individual device drivers into small, nimble Driver Domains means that device-related performance bottlenecks can be reduced or eliminated.  It also means that device drivers that might be subject to attack by crackers can be segmented from the rest of the environment and even refreshed regularly to remove any compromise that may be incurred.  Similarly, an unstable device driver can be isolated via disaggregation and easily rebooted if it should fail.

·         Flexible Virtualization Modes: The hypervisor provides different virtualization modes which allow the administrator to adapt to the specifics in the workload and capabilities of the hardware.  In particular, Xen pioneered the now popular concept of a paravirtualization (PV) mode offering an extremely optimized low-overhead experience for many workloads.

·         Multiple Architectures: The software can run on traditional x86 32-bit and 64-bit hardware (both with and without virtual extensions in the hardware), as well as on the new breed of ARM-based servers.  As your datacenter moves forward, your virtualization solution is prepared to move ahead with you.

·         Tool-Agnostic Cloud: The Xen Project was born with the concept that virtualization should be controllable in the manner which later came to be called Cloud Computing.  The availability of Xen Cloud Platform (XCP) and its associated programming interface (XAPI) ensure that you can control your VMs the way you want to, using whatever tool stack you choose.  Cloud technologies such as CloudStack and OpenStack can easily manipulate Xen VMs. There is no such thing as vendor (or project) lock-in to any one cloud solution.

·         Open Source: The Xen Project is now a Collaborative Project of the Linux Foundation, ensuring that the destiny of the project remains squarely with the community.  Yet, the impressive array of commercial project members ensures that substantial resources are marshalled for the continued development of Xen.

·         Moving Forward: The Xen Project continues breaking new ground with incubation projects such as Mirage OS, which will produce certain tiny, highly efficient VMs utilizing exokernel technology.

Clearly, there are lots of reasons to use Xen.  Maybe the better question is, “Why not use Xen?”

Russell Pavlicek is a Xen Project Evangelist who works for Citrix Systems. Introduced to Linux in 1995, he has been an Open Source columnist, speaker, author, and radio personality.