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Hyper-V R2 SP1 boosts guest support for Windows 7

Is 5:00 p.m. on a Friday too late for a little Hyper-V-centric news? Nah.

Microsoft’s Michael Kleef just posted a short update on his personal TechNet blog about a new discovery involving Hyper-V R2 SP1. Apparently, the latest version of Hyper-V will now support up to 12 virtual machines per logical processor, up from the previous max of eight, but only for Windows 7 SP1 guests.

In other words, admins can host up to 12 guest operating systems per logical processor on a Hyper-V host as long as each of those guest OSes are running Windows 7 SP1. Otherwise, the ratio of VMs/logical processor remains at 8:1.

The concept of “VMs per logical processor” is a sort of confusing one, however, as most admins are more familiar with VMs per core. One commenter on Microsoft’s requirements and limits page for Hyper-V even pleaded that the company change its lingo, noting that “while [logical processors] might be technically correct, what really matters is virtual processors per physical cores. This is a much easier concept to grasp.”

For his part, Kleef attempted to clear up the confusion in his post. He noted that “[Microsoft doesn’t] really support VMs/core…we actually support VMs/logical [processors]”, explaining that the term core implies “physical core support”, while logical processors “can be either physical or multi-threaded cores.”

Of course, he also added to the confusion by writing “Hyper-V SP1 increases support for VM/core” right in the title of the blog post, but still…

For more information on the first service packs for Windows 7 and Server 2008 R2, visit

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