Virtual appliances that can run in any virtual environment. It sounds almost like a campaign promise. But to realize that promise, someone has to give developers tools to build those appliances. That’s what Citrix says it will deliver in the next couple months with Project Kensho: tools that ISVs and in-house IT staff can use to create application machines that will run in any of the virtual environments, be it VMware ESX, Citrix XenServer, or Microsoft’s Windows Server 2008 Hyper-V.

Actually, along with the tools, you need some kind of standard blueprint, and that’s what proponents say the Open Virtual Machine Format (OVF) provides. “OVF offers a hypervisor-independent portable virtual machine format that packages a complete application workload with its resource requirements, configuration and customization parameters, and licensing information,” says Simon Crosby, chief technology officer of the Virtualization and Management Division at Citrix (citrix.com), and a member of the group that drafted the OVF specification. “Virtualized datacenter workloads captured in OVF format can be installed and run on any virtualization platform that complies with the standard. When a virtual machine is installed, the application is localized and optimized for that particular environment.”

Drafted originally by Citrix and VMware, and introduced last fall, OVF has “support and contributions” from Microsoft, IBM, and Dell, and has been adopted for standardization by the Distributed Management Task Force. As the DMTF officially explains it, OVF “uses existing packaging tools to combine one or more virtual machines together with a standards-based XML wrapper, giving the virtualization platform a portable package containing all required installation and configuration parameters for the virtual machines. This allows any virtualization platform that implements the standard to correctly install and run the virtual machines.”

Crosby says that at a recent DMTF event, “we used Project Kensho to create virtual machines from VMware, XenServer, and Hyper-V in the OVF format. We were also able to import and run OVF appliances on both XenServer and Hyper-V.”

Better Containers

If, like some people, you visualize virtual machines as little canisters, the way Citrix describes it you might think of Kensho-built OVF containers as being more like kegs.

“Some virtual machines are nothing more than a virtual hard disk,” Crosby says. “But OVF virtual machines are containers that can include everything needed to run an application workload. A container can include different kinds of applications, perhaps a database server and a Web server. OVF will allow a package to contain all the elements needed to accomplish a task, including any installation instructions, your networking components, application logic, everything.”

These containers can be out there in the cloud or on the network for others to download and use. This is part of the picture Crosby paints when describing the post-Kensho future: vast libraries of innovative apps or services that can be rented, bought or used for free. Because OVF specifies procedures to check the integrity of virtual appliances, Crosby says, appliances developed by third parties can be checked for security problems before being deployed.

OVF and Project Kensho tools will “solve the difficult interoperability issues between virtualization platforms while also eventually allowing automated provisioning,” Crosby says. “Enterprises and ISVs will be able to use any OVF packaged application workload. It doesn’t matter whether they use XenServer, VMware ESX, or Hyper-V. The workload will install and run on any of these environments that implement the standard.”

Large and medium enterprises that are “increasingly wary of the pitfalls of VMware vendor lock-in will greatly benefit from frictionless transition” between the different virtual infrastructures, says Ravi Gururaj, founder and CTO of VMLogix, whose LabManager application can leverage the Citrix, VMware, and Microsoft virtualization platforms.

OVF in Action

Replicate Technologies develops tools for managing the virtualized and physical networks that underlie a virtual machine environment. Replicate currently uses OVF to speed installation of its software solutions; products are delivered as virtual machines in OVF packages that run under VMware Virtual Center. (The company plans to target other hypervisor platforms.)
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“Replicate's tools install much more quickly and with less user intervention with the OVF ‘wizard’ in VMware Virtual Center,” says Ken Novak, chief architect at Replicate. “In the long run, our system discovery tools will read the OVF description of applications as a way to understand their needs and their impact upon the virtual environment.  This will apply to OVF descriptions of both acquired software and site-recovery in-house software applications.”

Although not using Project Kensho tools (Replicate builds its OVF packages with VMware tools), Novak sees significant benefits coming from OVF, in general.

“OVF can be extended to provide a more complete description of application architecture and requirements. Once extended, OVF will allow datacenter operators to: one, install applications much more rapidly; two, migrate applications from normal operations onto standby hardware or disaster-recovery datacenters; and, three, enable application vendors to deliver software in a package that is independent of hardware, guest operating system, and virtualization or cloud-computing platform, which should provide significant economies for both vendor and customer.”

Novak sees a future similar to that described by Crosby when discussing Kensho’s benefits, in which OVF containers carrying complete applications and required plumbing can be grabbed and deployed on-demand, and managed as just another component running in the datacenter.

“Many virtual machines are available both as downloadable appliances and as by-the-hour units of cloud computing,” he says. “Vendors like rPath have shown how to automatically embed applications into virtual appliances or cloud images -- for example, VMware or Xen or Amazon EC2. Clouds that directly support OVF applications will have the advantage of being able to directly utilize the software that has been developed for enterprise virtual infrastructures.”

The ability to create “packages of multi-tier applications comprising several server images as an appliance” designed to run in a virtual environment is “great enough without any consideration of crossing the boundaries of interoperability between virtual machine environments,” says Replicate’s CEO, Rich Miller.

Unchained

“As virtualization becomes even more mainstream in enterprise IT,” Crosby says, “organizations need to be able to take advantage of it without being tied to a single hypervisor or virtual disk format, a freedom that OVF allows.”

“The capabilities delivered by the Kensho tools will facilitate the rapid build-out of virtual datacenters that are platform-agnostic, heterogeneous, and standards-based,” says Gururaj of VMLogix. “Organizations will see the cost savings by not having to invest in different tools that do the same thing on different platforms. In fact, this may accelerate the adoption of virtualization as it removes some of the barriers to achieving truly agnostic IT infrastructures.”

Project Kensho tools are slated to be available for free download from Citrix in the third quarter, Crosby says. How soon after that we see application containers that can run in any virtual environment cannot be predicted.