Even though Citrix Systems XenServer is now free, solutions providers still need to know how to obtain a XenServer license. For you to implement a complete XenServer package, your customer will likely
The heart of XenServer is the Xen hypervisor, the virtualization component that runs and manages virtual machines (VMs) in your customer's environment. The Xen hypervisor is open source, and that means that not only is the hypervisor free, but you can also read its code. As a result, different vendors, such as Oracle, Novell and Citrix, are including the Xen hypervisor in their products. But you should note that a hypervisor alone cannot be used to create VMs. The hypervisor is just a kernel, and you need more components to actually do something with it.
Focusing on Citrix, the company currently offers XenServer 5.5, a complete operating system (OS) that allows you to create and run VMs. Even though XenServer is free, it must still be registered. After registration, you'll receive the XenServer license keys by email. Once you have imported the XenServer license keys in XenCenter, your customer's server is registered and completely activated.
XenCenter is the free management tool that comes with XenServer and allows you to perform basic management tasks. There's no additional registration procedure for XenCenter. Just download it from the Citrix website, install it on a Windows workstation and you are ready to go. XenCenter is excellent for creating a basic virtual environment with one or two servers running a few VMs. You can even perform advanced tasks from XenCenter, such as moving a VM from one host to another with the Live Motion feature.
If your customer needs advanced features, it must buy Citrix Essentials. This product, which exists for XenServer and Microsoft Hyper-V, allows you to perform more advanced tasks, such as high availability, workflow orchestration, dynamic workload balancing and more. You have to buy a XenServer license for every server you want to manage with this product. Solutions providers can find it at the Citrix store, where you pay $2,750 for the Enterprise edition and $5,500 for the Platinum edition (per server per year). In case your customer is not sure if it's worth the expense, you can get a free trial XenServer license that is valid for one month at the Citrix website.
Using Citrix products, solutions providers can build a decent virtualization offering for free. You will, however, miss the high availability feature, which makes sure that VMs automatically fail over to a remaining host if your customer's primary XenServer host goes down. If you prefer to do the failover manually, you can use the Essentials pack and build a complete and stable management environment for free.
About the expert
Sander van Vugt is an independent trainer and consultant living 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 February 2010