Late last week, Microsoft released Windows Server 2008 Hyper-V to manufacturing, or at least to the Web, providing Server 2008 customers with the first non-beta version of its hypervisor-based virtualization platform. A few things have changed since the beta, so I'd like to discuss those changes here, while raising one question about a potentially confusing and related product.

First the question. Server 2008 Hyper-V should not be confused with a related product called Microsoft Hyper-V. The former is a feature of Server 2008 that Microsoft released to manufacturing last week. The latter is a separate product that Microsoft doesn't really want to discuss right now. I find this vaguely irritating, but I'm told it will ship by the end of the year. More to follow. My question is this: What does a version of Hyper-V look like sans Server 2008? We'll have to wait and see.

Regarding the release to manufacturing (RTM) version of Server 2008 Hyper-V, or what I'll simply call Hyper-V from here on out, Microsoft says it's now ahead of schedule, which is a bit off-putting to those of us who remember when the company delayed its release past the general availability of Server 2008. But Microsoft had previously committed to shipping Hyper-V within 180 days of Server 2008; last week's release means the company did so with more than a month to spare.

Microsoft has improved the number of supported guest OSs in the RTM version of Hyper-V, but suffice to say the list looks like a who's-who of current and recent Windows and Windows Server releases. Here's what you really need to know: In the Hyper-V world, all guest OSes receive what's called "driver enlightenment," a low-level software connection between Hyper-V and the guest OS's virtualized hardware drivers. But only a handful of guest OSs receive "kernel enlightenment," which opens up better performance and interaction between the environments. Only Server 2008 and Windows Vista with SP1 get kernel enlightenment as guest OSs, as will all future Windows versions.

Virtual processor support is a related side issue, with newer Windows versions getting better multiprocessor support when used as guest OSs in Hyper-V. Server 2008, for example, can be configured with one to four virtual processors, whereas Windows 2003 supports just two (and the x64 versions of Windows 2003 support just one).

Microsoft is only explicitly supporting one Linux distribution as a guest OS under Hyper-V: SuSE Linux Enterprise Server 10 with SP1 or SP2, in both x86 and x64 variants. (Thus, Microsoft counts this as four different guest OSs.) If you want to run a different OS, you're on your own, although third parties are expected to provide the necessary integration components, using those for SuSE as a starting point.

Performance is dramatically better than expected. According to independent tests by QLogic and Intel, virtualized Hyper-V environments operate nearly as efficiently as physical servers with regards to Fibre Channel and iSCSI utilization and scaling between two- and four-socket systems. Microsoft says that using Exchange Server 2007 under Hyper-V requires identical configurations under Hyper-V as it does on real hardware, which is good. But it won't have a formal set of best practices documentation and support guidelines available for 60 days.

I've written a lot more about the Hyper-V RTM on the SuperSite for Windows, and of course a lot of questions remain. I'm interested to see how Hyper-V performs in the real world and should be speaking with some customers using it in production soon.

Hyper-V RTM Download