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Hyper-V: Life in the Slow Lane

Ben Armstrong, Microsoft's "Virtual PC Guy", has responded to an apparently growing number of reports about slow operating system installations of Microsoft's Hyper-V hypervisor.

Apparently, loading an OS into a Hyper-V-created virtual machine (VM) is like trying to get around the Washington D.C. beltway at 7:30 a.m. on a rainy Monday morning -- bring a book to read, because you aren't going anywhere fast. The problem, Armstrong relates, is that the emulated devices loaded with the OS were optimized to work with Microsoft Virtual Server, but due to Hyper-V's different architecture, that optimization has been removed. (Emulated devices are things like network adapters and mice that the host OS virtualizes. Emulation adds a lot of processor overhead, reducing performance.)

Microsoft decided not to re-optimize these emulated devices because it's moved to a new model with Hyper-V, that of synthetic devices. Synthetic devices are virtualization-tuned and work much faster than their emulated brethren. Synthetic devices, however, are installed after the OS is up and running; so during the installation process, non-optimized emulated devices are being used instead of the speedy synthetics.

Once loaded, the VMs work fine, and are faster than similar VMs in Virtual Server, according to Armstrong; it's just that putting them in place is laborious.

Armstrong says that this issue isn't likely to change for the first version of Hyper-V, so you're stuck with it for awhile.

Is this a big deal? It's hard to know initially. But one poster who responded to Armstrong's blog says it will: identified as "Xepol", the poster wrote, "Slow as molasses OS installs are a definite barrier to adoption. Might want to seriously consider that before calling any decission "final"."

What say you? Have you experienced this problem? If so, I'd love to hear from you.

Posted by Keith Ward on 02/27/2008 at 12:48 PM


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