The interoperability agreement has been forced on the two companies, which are not exactly natural allies or even particularly friendly even if they are mostly civil, by their respective customer bases, software partners, and resellers, explained Mike Evans, vice president of corporate development at Red Hat, and Mike Neil, general manager of virtualization strategy at Microsoft, in a webcast this morning.

The Red Hat-Microsoft deal is short and sweet, and bears little resemblance to the landmark interoperability, licensing, and patent protection deal that Red Hat rival Novell signed with Microsoft in November 2006.

That deal irked plenty in the open source community because of licensing issues relating to Linux and the applications that ride atop it. But it has boosted Novell's financials, with Microsoft buying hundreds of millions of dollars in licenses for SUSE Linux Enterprise Server 10 and distributing them to its Windows customer base.

Testing times

The two Mikes were at pains in the short announcement to make it clear that all that Red Hat and Microsoft have agreed to do were to test, validate, and jointly support each others operating systems when running on each other's server virtualization hypervisors. Red Hat's Evans said the agreement has no provisions for patent rights, or open source licensing, or any financial arrangements beyond the standard testing and qualification fees that Red Hat and Microsoft charge their ISV partners to get certified and an agreement to work together to provide cooperative support for products.

Virtualization is, according to Evans, moving out of the early adopter stage and into mainstream use in data centers. It is still early in the server virtualization game on x64 iron, but both Red Hat and Microsoft think that the lack of an interoperability arrangement between the two companies has been hindering the adoption of server virtualization.

Better virtualization management tools are available now, and the underlying x64 iron is able to do more sophisticated support for memory and I/O as it relates to virtual machines and their hypervisors. And with Gary Chen, research manager for enterprise virtualization software at IDC calculating that Windows and RHEL comprise 80 per cent of all guest operating systems on virtualized servers, now is the time for Red Hat and Microsoft to bury the hatchet. Well, it is more like a paring knife. But you get the idea.

As part of the deal, Microsoft is now a partner in Red Hat's virtualization certification program, and Red Hat has joined Microsoft's server virtualization validation program. The latter was set up by Microsoft last June, and includes Cisco Systems, Citrix Systems, Novell, Oracle, Sun Microsystems, Unisys, Virtual Iron, and VMware; so far, only Cisco, Citrix, Novell, and VMware have fully validated their programs with the Windows stack.

Microsoft will certify Red Hat Enterprise Linux 5.2, and 5.3 will run as a guest operating system on its Hyper-V hypervisor, which is associated with Windows Server 2008; both 32-bit x86 and 64-bit x64 servers will be certified, apparently. And Red Hat is to certify that Windows 2000 Server SP4, Windows Server 2003 SP2, and Windows Server 2008 will all run Red Hat's virtualization hypervisor inside Red Hat Enterprise Linux.

Hypervisor

While Evans did not say it by name, the open source Xen hypervisor is still the default hypervisor with RHEL 5. But with RHEL 6, Red Hat is expected to shift to its own KVM hypervisor, which it acquired last summer when it bought Qumranet. KVM is part of the mainstream Linux kernel, while Xen is not.

But Microsoft already has experience supporting Xen, through its agreements with XenSource, which sponsored the Xen project and which was acquaried by Citrix Systems two summers ago. Presumably, the deal calls for Red Hat to certify Windows Server instances running atop Xen now with RHEL 5 and atop Xen and KVM in RHEL 6. Anyway, Windows guests will be certified atop RHEL in the second half of this year.

Red Hat has a partnership with VMware that validates RHEL runs on its ESX Server hypervisor, but thus far, Red Hat does not have a similar deal with Citrix for its XenServer commercial version of the Xen hypervisor. Mainly because it sells its own implementation of Xen, which it wants customers to use.