Citrix Tools Show Virtualization Isn’t All About The Hypervisor

Citrix systems is preparing a set of free tools that illustrates how rapidly the virtualization market is maturing and how much it's changing the data center. The move also suggests where competition in virtualization will get most intense.

The Kensho Project tools are slated to become available in September and will focus on enabling workloads based on an emerging standard called Open Virtual Format. When built with OVF tools, a virtual workload can run under any hypervisor.

That neutralizes the hypervisor as a vendor lock-in and gives data center managers new flexibility in building virtual appliances and deciding where to deploy them. OVF will force suppliers to stop competing on whose virtual machine gets generated, and instead shift the race toward who's building the most flexible, manageable virtualized environment.For example, a virtual machine using Microsoft's Hyper-V hypervisor, and consisting of Windows and a Windows application assembled to the OVF spec, can run under Citrix XenServer or VMware's ESX Server--and vice versa. That's why, although Citrix made the first big move, "all the vendors are interested in OVF capabilities," says Forrester Research analyst Frank Gillett.

The Citrix tools will convert virtualized files into Microsoft's Virtual Hard Disk format, which is used for formatting a virtual machine as a set of files stored to disk. The tools capture application and virtual machine configuration data in an XML schema set by the Distributed Management Task Force, the standards body that ratified OVF, says Simon Crosby, Citrix's virtualization CTO and XenSource's founder.

VMware actually proposed OVF as a standard. VMware saw rivals Microsoft and Citrix align around Microsoft's VHD. While VMware's VMHD is the industry's dominant format, the company risked being typecast as a lock-in risk, or even a backwater, if VHD became more widespread. So VMware proposed OVF in February 2007 as a standard and embraced building virtual appliances so that each workload had its own VM, operating system, and applications. XenSource--the open source company built around the open source Xen hypervisor--agreed to co-author the draft standard, and other vendors, including Dell, Hewlett-Packard, IBM, and Microsoft, joined in. Citrix bought XenSource in August 2007.

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OVF fits the world of service-oriented architecture. It goes beyond previous formats that defined how a VM is stored to disk, letting multiple virtual files be assembled into one virtualized appliance, in case a service needs to be generated from different combinations of operating systems and applications. "OVF gives the IT manager real flexibility in choosing the course that suits the need," says Andi Mann, virtualization consultant at Enterprise Management Associates.

In announcing its Kensho tools ("kensho" means "enlightened experience" in Japanese), Crosby emphasized Citrix's commitment to interoperability. With VMware dominating virtualization, Citrix has every reason to make it easier for managers to move workloads from VMware to XenServer. In that sense, Kensho means an off-ramp from a competitor's product.

But if it lives up to its advance billing, OVF could just as easily be on-ramp to VMware's Virtual Infrastructure 3, its platform for managing VMs. The whole goal is to make moving virtual workloads a two-way street.