Citrix Promises Tool for Creating Hypervisor-Agnostic Virtual Appliances

Published: July 16, 2008

by Alex Woodie

Citrix Systems this week unveiled plans to allow users and ISVs to create "virtual appliances" based on the Open Virtual Machine Format (OVF) draft standard that can be deployed to most hypervisors. "Project Kensho," as the development effort is called, will result in a virtual appliance tool that supports the three main X64 hypervisors on the market--Microsoft's Hyper-V, VMware's ESX Server, and Citrix's own Xen. A preview of the tool is due by September.

The advent of virtualization software and hypervisors has given IT managers a great deal of flexibility in how they dole out workloads among their standards-based X86 and X64 servers. Like their mainframe, AS/400, and Unix brethren before them, administrators of X86 and X64 Windows and Linux systems now have the power to carve up their multi-processor servers into separate and secure operating environments, which has boosted server utilization rates to new heights and relegated the old "one box, one application" mantra to the scrap heap of IT history.

But virtualization, by itself, is not a panacea for total data center efficiency, and administrators are now grappling with a set of new issues stemming from virtualization and hypervisors. One of the problems has to do with portability and vendor lock-in. Namely, once you deploy a given hypervisor product, how easy is it to move your OS images--and the applications they run--off that hypervisor?

This is why VMware and XenSource (since bought by Citrix) proposed the OVF format in 2007. OVF describes how one or more VMs can be combined, using existing packaging tools, using an XML wrapper that includes all the required installation and configuration parameters for virtual disks, as well as physical CPU, memory, networking, and storage. This XML wrapper tells the hypervisor how the VM should be configured on the new machine, and is the secret sauce that is propelling OVF to be the new standard for deploying virtual appliances that can be freely moved about.

OVF is a good idea, and has the potential to revolutionize how operating systems and applications are consumed. (It could allow users to download pre-configured virtual appliances with hardened operating systems to their hypervisor-equipped servers.) That's why Microsoft, IBM, Hewlett-Packard, and Dell signed on with VMware and Citrix, and jointly submitted OVF to the Distributed Management Task Force for consideration as a standard. The DMTF accepted OVF as a draft standard last September.

VMware beat everybody to the punch last fall, when it shipped its OVF Tool, which converts OVF packages into the virtual machine format used by ESX Server and VMware's other virtualization offerings. Now Citrix is following up on that release with the promise of its own OVF tooling by the end of the third quarter. Only a technical preview of the tool will be available at that time.

A Virtual Licensing Issue?

While Citrix's OVF tool will be able to create virtual appliances that can be deployed on XenServer, Hyper-V, and ESX Server, Citrix says the tool will bring "added value" to the hypervisor of its close partner, Microsoft. One example of this added value is a result of XenServer's use of CIM-based management APIs, which allow Microsoft's System Center Virtual Machine Manager to manage XenServer and any Windows-based virtual appliances that may be running under XenServer.

This could be a weak spot for VMware. In a technical FAQ on OVF on VMware's Web site, the company indicates that, while OVF can be used to package Windows-based virtual appliances, licensing issues could be a problem.

"IT organizations can create Windows-based virtual appliances for internal deployment of solutions," VMware says. "[However] software developers should always verify their licensing agreements prior to redistributing any third-party software."

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