Microsoft and Citrix agree on virtual machine standard

Posted by Rick C. Hodgin

San Francisco (CA) - At VMworld 2007, a major obstacle in virtual machine sharing apparently has been overcome.  Microsoft and Citix Systems have agreed to use Microsoft's Virtual Hard Disk (VHD) standard for virtualization machine storage.  This philosophy of sharing in the virtualization world will likely be the first of many to come as they hone in on a single, workable standard.


In x86 spaces, virtualization platforms by Microsoft and Citrix include Microsoft Virtual PC 2007 and Xen.  Citrix acquired Xen from a company called XenSource which they are currently in the process of purchasing.  The acquisition will be finalized in Q4 of this year.  Both companies have announced they're now committed to providing the best possible virtualization experience.  And settling on a single VHD standard will allow multiple virtual executives (called hypervisors) to run the same virtual machine.  The virtual machine's operating systems will work via a single set of data without proprietary software or protocols required.  A common, shared VHD standard like this will enable cross-platform virtual machine sharing abilities which are not possible today.

Microsoft has also announced they will extend the VHD platform to include a future version of its SoftGrid Application Virtualization.  Microsoft and Citrix will both begin collaborating on new and emerging virtualization technologies.  They wi'll also begin developing a more standardized set of administrator tools which should allow easier virtual machine management by end-users on both platforms.

The movement will allow both companies to leverage their existing product bases for more directly developed virtualization environments.  Citrix has a significant infiltration in the Fortune 500 companies and their software is designed to distribute any application anywhere.  Being able to target virtualized software environments directly through a common interface will allow their software developers to work more cooperatively within a virtualized environment.  It's a process called called paravirtualization, and it can increase program flexibility and usability when properly applied.

Shared visions like this open up doors that many other developers can now use.  There a wider virtual machine support base on the same standard.  Because of that they can invest resources toward creating software or hardware products for that standard.  It's something the virtualization industry needs much more of.

Microsoft has made their VHD format available since May, 2005.  In October, 2006 it was released via Microsoft "Open Specification Promise", which was a promise to everyone that their patented technology could be used for free forever.  The VHD holds not only the virtual machine's OS, data files and programs, but also the state of the machine.  Virtual machines can be paused, restarted and saved in a given configuration.  They do not require physical booting and they can be moved from physical machine to physical machine.  When running they operate at near native speeds (as if they weren't running virtualized).  The flexibility virtualization offers is the primary reason corporations are jumping on board with this emerging technology.