Microsoft has released a set of drivers to allow production versions of Red Hat to run on Hyper-V. The drivers, otherwise known as integration components, have some limitations, but they come with the full assurance that both Microsoft and Red Hat will support such an implementation.

Specifically the drivers support RHEL 5.2, 5.3, and 5.4. These drivers also support SuSE Linux Enterprise Server 10 SP2 x86 and x64, and SuSE Linux Enterprise Server 11 x86 and x64, but that's old news.

With much fanfare, Microsoft first submitted said drivers to the Linux kernel way back in July (its first, and so far only, contribution to Linux). Those drivers were already tested to work with Red Hat and, of course, SuSE. And in October, Red Hat and Microsoft announced that they were joining each other's virtualisation partnership programmes, and validated that their products worked on each other's virtual machines. So what took Microsoft so long to release these Red Hat drivers to the public?

Microsoft's Vijay Tewari, principal programme manager with the Windows Virtualization Team said that the delay had been caused by one issue: the two companies hadn't worked out a deal on who would support the Red Hat operating system if it was running as a Hyper-V guest. The support issue was solved a couple of weeks ago and the drivers were made public.

There are some limitations, however, Red Hat virtual machines running on Hyper-V are limited to a single virtual processor, which limits the size of the Linux workload. But Tewari said that this limitation isn't specific to just Red Hat. SuSE is also limited to one VP. The number of VPs varies for different versions of Windows Server, too. WS 2008 R2 VMs have access to four VPs, WS3003 gets 3. Tewari says that Microsoft is working on increasing the number of VPs for Linux servers on Hyper-V.

Second, the components themselves don't provide mouse support, although Citrix makes an add-on, Project Satori, that fixes this issue. The mouse works if you are physically accessing the server. But, without the add-in, isn't available if you RDP into the machine and launch the console of the guest operating system via your remote connection, says Tewari.

These drivers began life as the same ones submitted to the Linux Kernel in July, 2009, but, as those originals have been modified with patches and changes from the Linux community, the code bases between this download and the Linux kernel have forked. Microsoft has said that over the next few months, it will integrate them back into a single code base. But, says Tewari, the fork was inevitable because the Hyper-V drivers were submitted to the latest stable version of the kernel at the time, 2.6.32 (version 2.6.33 became available late last month). Not all the commercial distributions are using that release. These drivers support Red Hat based on 2.6.18 and 2.6.27, for instance.

As part of the work of reuniting the code again, Microsoft promises to include some enhancements, such as a fix for the mouse issue.

Red Hat has promised that the Hyper-V drivers will eventually become a native part of its distribution. That will in all likelihood occur whenever Red Hat upgrades its commercial product to kernel 2.6.32 or later. Indeed, this is the reason why Microsoft swallowed crow and submitted its drivers to the kernel in the first place, under the GPL no less. This even though it continues to toy with the threat that Linux violates its patents. 

Until then this frienimies/odd couple needed to work out who was going to support what. In October, Red Hat certified that its operating system would work with Hyper-V, but Tewari says, that didn't mean that Red Hat was saying Hyper-V guests would be supported. A couple of weeks ago Red Hat agreed that the Hype-V drivers would be treated under the same policy that other third-party drivers not directly included in the distro were treated. Red Hat will now support its operating system, even if its running on Hyper-V, unless its support folks say the issue is caused by the driver. In that case, Microsoft will provide support.

If this whole situation still sounds less than ideal, Tewari asks users to stand by for a little while. He's got some upcoming news he says you'll like, "We understand the kind of support we offer for Linux with the ICs is not at the same level that we support Windows, but we are fully committed to make sure that our customers get that same support over time. You should be seeing an announcement from us in the next two to four weeks."