I recently posted the following in a forum topic comparing VMware ESXi and Microsoft Hyper-V hypervisors and thought I’d slap it here for posterity:
Hyper-V does not run as a service on top of Windows – which would be a Type 2 hypervisor, rather it is a Type 1 hypervisor (just like ESXi) that runs natively on the hardware. If one has installed the GUI/Core version of Windows Server 2008 R2 or 2012 (instead of the Hyper-V Server 2008/2012 products), then once the Hyper-V role is enabled, that OS is “virtualized” into the Parent Partition as a part of that process (one of the reasons for the required reboot). This Parent Partition is a virtual container that must go through the hypervisor (Hyper-V) to access the hardware, but it is not visible in the Hyper-V Manager or SCVMM because it’s not a Child Partition (see http://en.wikipedia.org/wiki/File:Hyper-V.png). The attack surface for Hyper-V itself is minimal – similar to ESXi – and more likely penetrated via vulnerabilities introduced through misconfiguration – similar to ESXi. In addition, the attack surface of the OS in the Parent Partition can be sufficiently limited through the use of the Hyper-V Server 2008/2012 products or the Core install of Windows Server 2008 R2/2012. If the environment is managed through SCVMM (an all-inclusive management tool – similar to vCenter w/ added features) and PowerShell, then there is no need for a GUI at the Hyper-V host level – in fact, one might argue that it’s irresponsible to install a GUI at the Hyper-V host level due to the increased resource utilization (minimal, but there), attack surface and management (patching) requirement.
As for the comparison of the 2 major players (ESXi and Hyper-V), they each have their pros and cons that must be weighted based on the requirements of the target environment to settle on the best product for each target environment. To me, it’s a bit like choosing a mode of transportation; you wouldn’t want a Ferrari in Antarctica or a snowmobile in Miami. While each has its own pros/cons, the environment dictates the better choice… 😉
However, I will say that, in my opinion, Microsoft will likely penetrate the hypervisor market by leaps and bounds over the next several years if only because there are decidely more Windows-centric environments than any other OS, there’s more Microsoft-skilled labor out there, the price comparison is currently lobsided in their direction, the all-inclusive cloud-enabling management tool – SCVMM, cluster-aware updating via WSUS/SCCM and the flexibility/performance of SMB 3 for Hyper-V Clustering. One of the primary reasons I think Microsoft’s penetration of the market won’t be swift and overpowering (i.e. taking several years) is that VMware has been a leader for quite a long time, which means it will likely take hurculean efforts to convince VMware professionals to consider the alternative (bottom-up) and the existing investment in and ROI-projections for licensing and hardware (NFS-based SAN storage) for environments with a significant VMware footprint (top-down). But those speed bumps will likely be flattened as time passes and Microsoft continues to strengthen the Hyper-V solution, unless VMware comes off the ropes swinging with some serious R&D (technical) and a new pricing model (financial).
While I think the Hyper-V solution is compelling – especially considering the advancements in 2012, I also think that VMware vSphere is a solid/reliable product with a proven track-record and a well-trained, loyal workforce out there. Also, vSphere just makes better sense in some environment – as I said initially, each solution (and others Xen, KVM, QEMU, VirtualBox, etc.) has its pros and cons that need to be considered and weighted with requirements for each environment.
Additional MS References:
Hyper-V Architecture Poster: http://www.microsoft.com/en-us/download/details.aspx?id=29189
MS Virtualization Team Blog: http://blogs.technet.com/b/virtualization/
MS System Center Blog: http://blogs.technet.com/b/systemcenter/
MS Storage Team Blog: http://blogs.technet.com/b/filecab/
MS Jose Barreto’s Blog: http://blogs.technet.com/b/josebda/
MS Edge on Channel 9: http://channel9.msdn.com/Shows/Edge