The Microsoft and XenSource partnership

Posted by virtualization.info Staff   |   Thursday, August 3rd, 2006

Two weeks ago Microsoft and XenSource announced an agreement to grant interoperability of virtual machines on upcoming Windows Server Virtualization and XenEnterprise virtualization platforms.
The move raised the attention of the whole IT world, involving licensing, supporting, security and performance issues.

virtualization.info interviewed both companies to further understand details of the agreement and spread some lights on what customers have to expect for the Microsoft hypervisor release.
To answer questions I met Mike Neil, Senior Director of Virtualization Strategy, Windows Server Division, at Microsoft, and Simon Crosby, CTO at XenSource.

To simplify questions and answers since now we’ll call a virtual machine natively running on Microsoft hypervisor, Windows Server Virtualization, as WSV-VM and a Xen virtual machine natively running on XenSource hypervisor, XenEnteprise, as XE-VM.


Microsoft Side

virtualization.info: The WSV-VM running within XenEnteprise will have all capabilities it already has on Windows Server Virtualization or there will be some limitations?

Mike Neil: The technology resulting from this agreement will provide interoperability between Xen-enabled Linux guest operating systems running on Windows Server virtualization in Windows Server Longhorn. Windows guest running on XenEnterprise will continue to function in the same way they do today.
For customers with Premier-level support agreements, Microsoft will use commercially reasonable efforts to investigate potential issues with Microsoft software running in XenEnterprise or other non-Microsoft virtualization technology. Our product support policy is described here.

VI: The upcoming Virtual Machine Manager will be able to centrally manage XE-VMs along with WSV-VMs, including tasks like provisioning and live migration between hosts?

MN: The first release of System Center Virtual Machine Manager is focused on the management of Windows environments. That said, it will be able to centrally manage Linux guests.
Some of the things you can do with SCVMM and Linux guests are:

  • Deploy Linux VMs in VHD format from the central library
  • Configure the virtual machine parameters for Linux VMs, such as RAM and disk space
  • Control the state of the virtual machine (start/stop, pause/resume, save/restore)
  • Live migrate a running Linux VM from one physical host to another

These are features that are enabled by the System Center Virtual Machine Manager and Virtual Server 2005, or Windows Server Virtualization, and are not specific to the technology being developed as part of the XenSource agreement. Live migration of guests will be a feature for Windows Server Virtualization.

VI: Will Microsoft offer support for XE-VMs running on WSV? If so will it be equal to one offered for Linux guests natively created on WSV?

MN: We currently support Linux running as a guest in Microsoft Virtual Server 2005 R2 from both a technology perspective and a 24-hour technical support perspective. When we added the support of specific Linux distributions on Virtual Server 2005 R2, we made a long-term commitment to make sure that non-Windows operating systems can be run in a supported manner, both on top of Virtual Server and our future virtualization products. Proving support for XE-VMs on Windows Server Virtualization is a part of the commitment.

VI: In a scenario where a WSV-VM is moved on XenEnteprise hypervisor some critical issues raise about licensing and support.
If the Microsoft customer is using an unlicensed version of Windows inside the WSV-VM (which is permitted by the new virtualization licensing model up to 4 virtual machines), what will happen when he’ll run it on XenEnterprise? And who between Microsoft and XenSource will support the virtual machine on that case?

MN: The four virtual instances allowed with Windows Server 2003 Enterprise Edition are not unlicensed. They are in fact license rights granted for the Enterprise Edition. We also recently extended virtualization licensing rights to Windows Server 2003 Datacenter Edition, providing for unlimited virtual instances with that version of Windows Server.

A customer running Windows Server needs to acquire a license for the physical machine they are running Windows on, regardless of the virtualization technology they are using. If they are running a VM on XenEnterprise, they need to have acquired a license for that Windows machine as well. More details about Microsoft’s virtualization licensing policy can be found here.

As I mentioned above, for customers with Premier-level support agreements, Microsoft will use commercially reasonable efforts to investigate potential issues with Microsoft software running in XenEnterprise or other non-Microsoft virtualization technology.

VI: How much time the agreement will last?

MN: The agreement is to develop and deliver the technology for interoperability between Xen-enabled Linux guests and Windows Server virtualization, to be delivered around the same time Windows Server virtualization is delivered (within 180 days of Windows Server Longhorn, which is slated for release in H2 2007). That said, we do have an ongoing relationship with XenSource (they licensed Microsoft’s Virtual Hard Disk format, for example). We share a common goal to help customers more easily realize the benefits of virtualization.

XenSource Side

virtualization.info: Technically speaking what will happen exactly in the interoperable scenario, where a XE-VM will be executed by Microsoft Windows Server Virtualization hypervisor?

Simon Crosby: Our announcement of a strategic partnership with Microsoft will enable Xen-enabled Linux guests to run with full benefits of paravirtualization (Microsoft terms it enlightenment) on the upcoming Windows Hypervisor, code named Viridian. Viridian and Xen share a common architecture, and are both paravirtualizing hypervisors. This is key, because paravirtualization has been recognized as the most important enabler of virtualization by every OS vendor. This architecture will be supported in the next release of every x86 OS of relevance to the enterprise, with RHEL 5 and SLES 10 Linux incorporating Xen (indeed many other Linux distributions will do so too); Sun with a Solaris 10 update expected later this year, and Microsoft with Viridian. Viridian will ship as an embedded component of Windows Server Longhorn.

When the Xen-enabled Linux guest runs on Viridian, it will use the native Xen hypercalls to access virtualization functions. A small adapter will adapt the Xen hypercalls into Viridian hypercalls so that the Linux guest can run with full performance on this paravirtualizing hypervisor.
In addition, we are collaborating with Microsoft on the delivery of paravirtualizing I/O capabilities for Xen-enabled Linux guests to run on Viridian. These capabilities are called Virtualization Service Clients and Virtualization Service Providers in the Microsoft terminology, and they correspond to the Xen front end and back end drivers used for paravirtualized I/O.

VI: The XS-VM running within Microsoft WSV will have all capabilities it already has on XenEnteprise or there will be some limitations?

SC: To be clear: The Xen-enabled Linux will be exactly the same Linux as is shipped by Red Hat or SUSE, or whatever other distribution we support. This has nothing in particular to do with Xen Enterprise, which is XenSource’s product and which also supports those Linux guests. That is, all implementations of Xen will support these Linux guests, since all Xen implementations (including in Solaris, RHEL, SLES) support paravirtualized guests.

The answer to the question is thus: The Xen enabled Linux guest will have all of the capabilities that it has when running virtualized on Xen.

VI: In this collaboration will XenSource have full access to all Microsoft WSV software code? If not, how XenSource will be able to assure that performance and security levels of a XE-VM will be identical on both XenEnterprise and Windows Server Virtualization?

SC: The terms of the collaboration between XenSource and Microsoft have not been disclosed, however we certainly can state that we have a license from Microsoft to implement the adapter against the Viridian hypercall API. Microsoft has disclosed that API to several vendors, and discussed it in detail at the recent WinHEC conference.

VI: Is this agreement breaking in some way GPL license of Xen or Linux in general?

SC: Not at all. XenSource is committed to the GPL Xen code base as the key to our powerful community and the ubiquitous delivery of a uniform feature set. We lead the industry through open development, and every feature that is currently in development, that does not require a closed source license by virtue of a license agreement with a 3rd party, is targeted for GPL implementation.
It is XenSource’s intention, wherever possible, to deliver features into the open source Xen code base. In the specific case of our Microsoft partnership, some components cannot be released under GPL.

VI: Can we expect some support available to the open source community, from know-how XenSource will gain during this agreement?

SC: The benefits for Xen from our collaboration with Microsoft will be tremendous. We anticipate that we will be in a far better position to deliver high performance Windows support on Xen, and moreover Microsoft has agreed to support Windows on our own product, XenEnterprise.
More importantly, perhaps, is the recognition from Microsoft that Xen’s paravirtualization (enlightenment) is the hypervisor architecture of the future, as opposed to emulation and binary patching. It is a vindication of the technology leadership of the Xen community, of our open source collaborative development and ubiquitous deployment. It is an acknowledgement from the most powerful OS vendor in the industry, that the Xen hypervisor is the hypervisor to beat, and that the installed base is about to be consigned to history. A common architecture, supported by every OS vendor in the industry, is emerging.

Xen’s paravirtualization architecture has been endorsed by every OS Vendor, and this is a tremendous shot in the arm for every vendor in our ecosystem. Microsoft’s support of that will be of great importance to every vendor working on Xen – as it is a recognition that their investment in an open industry standard platform has been proven worthwhile.