After Citrix bought Xen in 2007, the core of this popular open-source hypervisor remained open source, but some of the rest became proprietary software. Now Citrix has decided to take all of its virtual machine manager and cloud XenServer software back to its open-source roots.

Citrix has announced that all of its XenServer 6.2 platform will be open-source software. Citrix isn't making these open-source moves because Xen isn't popular. Far from it.

Xen is the foundation of both the Amazon Web Services (AWS) cloud and Rackspace's OpenStack-based cloud. XenServer has customers.

So why commit everything, à la Red Hat, to open source?

For starters, Citrix already was moving in this direction. In April 2012, Citrix gave its CloudStack software to the Apache Software Foundation, and a year later Citrix put its core Xen project under the Linux Foundation's control .

This final move, Mark R. Hinkle, Citrix' senior director of the cloud computing community, explained in a blog, came about because, "Much of XenServer already was open source, leveraging packages from the Xen Project, Linux kernel and the XAPI Project. We believe that open source plays a strategic role in the future of virtualization and cloud technology and that only open source offers the opportunities for collaborative, open innovation and the economies of scale that these markets demand. By open sourcing XenServer, customers, partners and developers gain full public visibility into the ongoing development and future of XenServer and can directly engage with us to contribute new XenServer functionality, build deeper integrations and steer the architectural direction of the platform."

Hinkle continued, “This move will give XenServer users the best of both worlds, free software [with] commercial support available." For details on exactly which open-source license applies to every part of XenServer see the XenServer license page.

The XenServer code will be hosted on XenServer.org.

Hinkle concluded, "This is just the beginning of XenServer.org. We'll begin by releasing the source code and providing binaries for users to download and install. For now we'll provide mailing lists and still use the existing forums provided by Citrix. Over time we'll transition them to this site. Additionally, we'll add all the things that you would expect from an open-source project including a way to track bugs, request features and interact with the developers to collaborate on the code. We also include a number of ways to ask questions and get support via the mailing lists, forums and our Q&A system."

As for the latest 4.2 release, Citrix boasts it will have:

Massive Horizontal Scale and Increased Performance — XenServer 6.2 delivers best of breed capabilities while running 500 virtual machines and 4,000 virtual CPUs per host, and significantly improving boot storm performance. As a result, customers can drastically improve their desktop virtualization density and performance, and more easily future-proof their infrastructure for the cloud.

— XenServer 6.2 delivers best of breed capabilities while running 500 virtual machines and 4,000 virtual CPUs per host, and significantly improving boot storm performance. As a result, customers can drastically improve their desktop virtualization density and performance, and more easily future-proof their infrastructure for the cloud. Windows 8 and Windows 2012 Support — XenServer 6.2 leverages platform enhancements in Windows 8 and Windows 2012 to bring even greater server consolidation when virtualizing workloads.

— XenServer 6.2 leverages platform enhancements in Windows 8 and Windows 2012 to bring even greater server consolidation when virtualizing workloads. Desktop Virtualization Integrations — XenServer is already optimized for XenDesktop, offering IntelliCache, Dynamic Memory Control, lowest TCO and best-in-class performance. XenServer 6.2 continues to be optimized for desktop virtualization, adding new Desktop Director alerts for low resources (memory, CPU, disk, network) and preemptive actions to prevent hosts from becoming unusable.

For its commercial customers, Citrix's new support model is moving from a server-based licensing plan to a socket-based licensing plan. This support option will include packaged updates and maintenance, 24x7 worldwide support, and commercial license protections. Users can, of course, also just use the open-source XenServer for free with their own IT staff.

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