Hyper-V in WS08 R2 Release Candidate: Bringing More to the Table

Hyper-V in WS08 R2 Release Candidate: Bringing More to the Table

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You'll want to read Isaac's blog post about the RC milestone of Windows Server 2008 R2. His post focuses on 64 LP support and processor compatibility mode for live migration. Read the post here.

Here's an excerpt:

64LP Support

We have seen processors grow from 1, 2, 4, and now 6 cores on a single processor, soon to hit 8.  Within the Windows Server 2008 R2 lifecycle, 64 logical processor servers will become commonplace (8 processors x 8 cores).  Virtualization is the natural fit for these next-gen servers, allowing them to consolidate a greater number of virtual machines on a single host. Hyper-V is in line with these hardware trends all with an eye towards bringing you greater VM density. The dev team has done a fantastic job in building and testing a platform that can scale.

Let's take a quick look at the history of logical processor support for Hyper-V:

  • Server 2008 Hyper-V                                         16 LP Support
  • Server 2008 Hyper-V +update (KB95670)      24 LP Support
  • Server 2008 R2 Hyper-V Original POR           32 LP Support
  • Server 2008 R2 Hyper-V RC/RTM                   64 LP Support!

Processor Compatibility Mode for Live Migration 

Live Migration is the killer-feature in Windows Server 2008 R2!  Previous to the RC build of Windows Server 2008 R2, identical CPUs were needed across every node in the cluster in order to perform a live migration.  As we came closer to the RC milestone we got feedback from customers and partners asking, "What if I deploy additional nodes that contain newer processors with features not contained in the original nodes?"  Well, we've solved that problem due to tremendous effort by the Hyper-V development team.

Processor compatibility mode is very straightforward. It enables live migration across different CPU versions within the same processor family (i.e. Intel-to-Intel and AMD-to-AMD). However, it does NOT enable cross platform from Intel to AMD or vice versa. It works by abstracting the VM down to the lowest common denominator, in terms of instruction sets, which enables live migrations across a broader range of Hyper-V host hardware.

There are a few things to note: Processor compatibility mode is disabled by default but you can configure it on a per-VM basis. There are no specific hardware requirements other than the CPUs must support hardware assisted virtualization (i.e. Intel's IVT and AMD's AMD-V).


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  • Hi

    I would like more info on the cpu compatibility mode and abstracting the VM down to the lowest common denominator.

    Is this common denominator placed on the VM before start of the VM? Or is it more like the lowest cpu off all hosts that is set to be the lowest denominator and all VMs that belong to hosts in that group / cluster?? (I'm used to VMware terminology).

    If it is host based, what would happen if I remove the lowest host from that cluster, can I just lift the common denominator of that cluster?

    If it is VM based, would a VM running on host 1 have a different set of instructions when moved to host 2? And how would the OS/Application handle this?


    Gabrie van Zanten


  • Voici 2 énormes nouveautés qui arrivent avec la Release Candidate : Support de 64 processeurs logiques

  • Ieri sera si è tenuta la keynote di apertura di TechEd 2009 US, la principale conferenza tecnica annuale

  • Ieri sera si è tenuta la keynote di apertura di TechEd 2009 US, la principale conferenza tecnica annuale

  • I've blogged something about green features Windows Server 2008 R2 has to offer. Could you please shed some light on whether "Core Parking" is a reliable feature enterprises can really make use of?


  • Virtualization Nation, We were very busy last week with numerous virtualization announcements from TechEd.