XenServer was already available for free. What changes now that it's going open source?
You have to understand that "free" is not the same as "open source." XenServer became free earlier in 2009, which meant that you could use it without paying licensing fees.
The XenServer platform, on the other hand, consisted mainly of closed source software, meaning that it's not possible for programmers to analyze and modify the software code. This is going to change when XenServer becomes open source, however. Once that happens, other vendors that use Xen can access XenServer's code to enhance their own products.
Seeing as the Xen hypervisor is an open source product, how does an open source Citrix XenServer affect it?
It may appear that nothing has changed with this recent announcement, but that's not true. The Xen hypervisor is the core component of any Xen technology, which is used by vendors such as Novell and Oracle.
On top of the Xen hypervisor, though, you need an OS to tell it what to do. The OS not only allows virtual machines to run but also provides some basic management tools. So, with the open-sourcing of the XenServer platform, users will get the complete package and not just the hypervisor.
Does this mean that all Citrix software related to XenServer will become open source?
In addition to XenServer, Citrix provides management utilities as well. XenServer's transition to open source does not affect these utilities. There may be different reasons for that, however.
According to Crosby, the reason to open source XenServer is to make it easier for the Xen community to develop solutions for the Citrix Cloud Center -- in which XenServer plays a key role. But most of Citrix's management utilities don't play an important role in this.
XenCenter, for instance, offers an easy-to-use graphical management interface, but it's not essential for the Citrix Cloud Center. Therefore, its code as well as other tools and drivers will remain proprietary, (such as some Windows drivers that cannot be published as open source because of the Microsoft licensing model). Also, the XenServer physical-to-virtual migration utility (available for free) will remain proprietary.
What does Citrix hope to accomplish by making the XenServer platform open source?
XenServer will play a key role in the Citrix Cloud environment. By publishing the source code, Citrix makes development for their cloud environment easier, while helping XenServer gain greater market share.
Once XenServer becomes open source, does that spell trouble for other vendors that sell Xen solutions?
An open source Citrix XenServer makes the Xen community stronger. Soon, any vendor will be able to access XenServer's source code -- which will help them enhance their software.
Xen vendors can still make money through management tools, however. In this regard, nothing will really change.
About the expert
Sander van Vugt is an independent trainer and consultant based in the Netherlands. Van Vugt is an expert in Linux high availability, virtualization and performance and has completed several projects that implement all three. He is also the writer of various Linux-related books, such as Beginning the Linux Command Line, Beginning Ubuntu Server Administration and Pro Ubuntu Server Administration.
This was first published in January 2010