Xen – KVM – Linux – and the Community

At Xen Summit last week, several community members and I discussed the issues around the recent launch of RHEL without Xen and its implications for Xen and the Xen.org community. I thought that I would share my opinions with a wider audience via this blog and hopefully get feedback from the Xen community on this important topic. So, feel free to comment on this post or send me mail privately if you wish to express your opinion to just me.

Firstly, I would like to offer my congratulations to the KVM community for the successful launch of their solution in Red Hat 6 shipping later this year. We in the Xen.org community are very supportive of all open source projects and believe that innovations made in the Linux kernel for virtualization can equally be shared by KVM and Xen developers to further improve open source virtualization hypervisors. I look forward to KVM and Xen working together to ensure interoperability, common formats, and management interfaces to provide customers with the maximum flexibility in moving virtual machines between hypervisors as well as simplifying overall virtualization management infrastructure. Xen.org is currently promoting the DMTF management standard for virtualization and cloud computing and welcome the KVM community to join with us by leveraging our OVF and DMTF SVPC implementations.

Many Linux community members and technology press have been busy the past few weeks writing off Xen as no longer relevant based on the launch of KVM. I have enjoyed reading the many articles written about this and thought I would add some insight to help customers, companies, and journalists better understand the differences between KVM and Xen. KVM is a type-2 hypervisor built into the Linux kernel as a module and will ship with any Linux distribution moving forward as no work is required for the Linux distributions to add KVM. Having a virtualization platform built-in to the Linux kernel will be valuable to many customers looking for virtualization within a Linux based infrastructure; however these customers will lose the flexibility to run a bare-metal hypervisor, configure the hypervisor independent of the host operating system, and provide machine level security as a guest can bring down the operating system on KVM. Xen, on the other hand is a type-1 hypervisor built independent of any operating system and is a complete separate layer from the operating system and hardware and is seen by the community and customers as an Infrastructure Virtualization Platform to build their solutions upon. In fact, the Xen.org community is not in the business of building a complete solution, but rather a platform for companies and users to leverage for their virtualization and cloud solutions. In fact, the Xen hypervisor is found in many unique solutions today from standard server virtualization to cloud providers to grid computing platforms to networking devices, etc.

To get a better understanding of how Xen.org operates, you must understand what the mission and goal of the Xen.org community is:

  • Build the industry standard open source hypervisor
    • Core “engine” in multiple vendor’s products
  • Maintain Xen’s industry leading performance
    • First to exploit new hardware virtualization features
  • Help OS vendors paravirtualize their OSes
  • Maintain Xen’s reputation for stability and quality
  • Support multiple CPU types for large and small systems
  • Foster innovation
  • Drive interoperability

This mission statement has been in place for many years in Xen.org and is an accurate reflection of our community.  It is our most important mission to create an industry standard open source hypervisor that is a core engine in other vendor’s products. Clearly, Xen.org has succeeded in this mission as many companies including Amazon, GoGrid, RackSpace, Novell, Oracle, Citrix, Avaya, Fujitsu, VA Linux, and others are leveraging our technology as a core feature in their solutions. It is not the intention of Xen.org to build a competitive packaged solution for the marketplace, but rather create a best of breed open source technology that is available for anyone to leverage.  This distinction is critical to understand as many people are confused as to why Xen.org does not compete or market against other technologies such as VMWare, HyperV, and KVM. Our goal is to create the best hypervisor possible without any focus on creating a complete packaged solution for customers. We embrace the open model of allowing customers to choose from various solutions to create their optimal solution.

Xen.org also spends a great deal of developer effort in performance testing as well as ensuring that we leverage efforts from hardware companies such as AMD and Intel to support the latest available hardware technologies. For example, Xen 4.0 supports the latest in SR-IOV cards which are just now being shipped to customers.

The third bullet on the mission statement can now be checked off as Xen.org has been instrumental in the efforts to upstream DomU paravirtualization software into the Linux kernel so all Linux distributions are now available for paravirtualization with no user changes required.  Xen.org is also working to upstream changes for our Dom0 kernel  to Linux and is being led by Jeremy Fitzhardinge and Konrad Wilk who recently updated the community on their work at Xen Summit; slides here. As Xen is not written as a Linux module or specially for Linux only deployments, it takes additional efforts to properly include Xen dom0 support into the Linux kernel. The community is always open to new contributors to assist Jeremy and Konrad on their development project and can contact me for next steps.  Finally, it is worth remembering that a Dom0 for Xen can run on NetBSD, FreeBSD, Solaris, or other operating system and is not a Linux only solution. Xen continues to embrace the customer choice model in Dom0 operating system selection which is part of our core mission.

The remaining bullets also reflect what you see in Xen.org as we look to support customer choice in all computing elements as well as ensuring that Xen.org leads the industry in pushing the envelope in new features for hypervisors.

As you can see, Xen.org’s mission is not to create a stand-alone, Linux-only competitive product that is a single packaged offering for end-users. Instead, we focus exclusively on building the best open source hypervisor technology in the marketplace and allow others to leverage our technology in any manner they wish with a maximum amount of flexibility for processor choice, Dom0 operating system , DomU virtualization, management tools, storage tools, etc. This flexibility along with  technology capability is a competitive advantage for customers and companies that choose Xen. Going forward, the Xen.org community will continue to focus on these goals as we include our new Xen Cloud Platform project  and Xen Client Initiative into the technology deliverables from our open source community.