Microsoft's tolerance for Linux expanded today via an alliance with open source server virtualization backer XenSource.

Microsoft has pledged to let "Xen-enabled" Linux guest operating systems run on top of the virtualization software that will ship with "Longhorn" Server and to provide technical support for the guest OSes. The agreement to support Linux guests in partnership with XenSource builds on Microsoft's decision in April to provide technical support for Linux running on its own Virtual Server partitioning product. The deal also tightens the bond between Microsoft and XenSource, as the two vendors look to gain market share against clear server virtualization leader VMware.

It's nothing short of heart-warming to see how much VMware bothers Microsoft.

The software giant first bought Connectix, believing that Virtual PC and Virtual Server would let it challenge VMware. That plan hasn't worked out so well. Microsoft this year decided to give away its virtualization products for free and, as mentioned, has gone so far as to embrace Linux in order to keep up with VMware and customers.

Starting with Longhorn Server, Microsoft plans to scrap its current Virtual Server attack and release hypervisor technology that should boost the performance of its server virtualization products and bring it closer to rival products from VMware and XenSource. Microsoft today said it expects Longhorn Server to ship at the end of 2007 and for the new hypervisor - code-named Viridian - to ship "within 180 days" of the server software. So, happy waiting.

In the meantime, XenSource looks to keep going after Windows customers. The company has released a version of Xen fit for Windows boxes and, unlike VMware, has a license for Microsoft's Virtual Hard Disk format. The end result of the licensing deal is that customers can shift virtual operating system images from Virtual Server over to Xen.

Why would Microsoft be so friendly with XenSource and Linux?

Well, there's no way it can truly compete well in the server virtualization market until that update to Longhorn Server ships. Microsoft appears ready to promote XenSource in the interim if that means trouble for VMware.

Microsoft SVP Bob Muglia put it another way. "Microsoft’s commitment to customers is to build bridges across the industry with solutions that are interoperable by design. Our work with XenSource, a recognized leader in open source virtualization technology, reflects that commitment and Microsoft’s ongoing efforts to bring virtualization solutions to the mainstream and help customers progress toward self-managing dynamic systems.”

Microsoft's plan to bundle its next-generation hypervisor with Windows Server at no charge has caught the eye of many curious server industry watchers. Perhaps a Linux embrace will remove some of those familiar bundling feelings that have caused so much trouble in the past. ®