Update: I removed some of the links in the article because Greg Shields gave up his blog.

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Greg Shields published an interesting article that explains the difference between the hypervisors of Microsoft's Hyper-V and VMware's ESX. It is a response to a widespread misunderstanding. VMware supporters tend to believe that VMware ESX has a bare metal hypervisor, whereas Hyper-V runs like Microsoft Virtual Server 2005 on top of Windows. Greg explains in detail in what sense both virtualization solutions are Type 1 hypervisors contrary to Virtual Server and VMware Server, which use Type 2 hypervisors. A Type 2 hypervisor is installed on top of the administrative OS, whereas a Type 1 hypervisor runs on bare metal, a layer below the administrative OS (Windows Server 2008 in the case of Hyper-V and Red Hat in the case of ESX).

However, there are also important differences between Hyper-V's and ESX's hypervisors. Greg makes things absolutely clear: Hyper-V has a far more advanced hypervisor because it is microkernalized, whereas ESX has a monolithic hypervisor. Among other things this means that Hyper-V uses synthetic device drivers, which are just pointers to the real device drivers into the primary partition's administrative OS (Windows Server 2008). ESX's device drivers exist within its hypervisor. Hyper-V's architecture has quite a few advantages:

  • Hyper-V's smaller microkernel improves performance
  • Hyper-V supports paravirtualization, which improves the performance of supported guest operating systems
  • ESX monolithic hypervisor leverages hardware emulation, which makes it slower
  • ESX's kernel has a higher complexity, which makes it more prone to errors
  • Supporting new devices is more time consuming for VMware because drivers have to be integrated into the kernel
  • Hyper-V supports more devices because it relies on Windows devices drivers

The fact that Hyper-V's administrative OS in the parent partition is a full-blown Windows Server 2008 installation and therefore is much bigger than in ESX's case is no disadvantage because disk space is not an issue these days. The mere size of the parent partition has no negative effect on the hypervisor's performance.

This is certainly true, but I'd like to add that the mere presence of all this Windows code in the parent partition increases the attack surface. Considering that Windows is more widespread than Linux, ESX is probably the more secure virtualization solution. Furthermore, Hyper-V's reliability depends more on third party device drivers.

Greg acknowledges that Hyper-V plus Virtual Machine Manager lack some important management features compared to ESX and Virtual Center. I think there is still a long way to go for Microsoft to catch up with VMware in this area. However, Microsoft is already ahead as far as the hypervisor, which is the core of any server virtualization solution, is concerned.

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Please check out Greg's article about the differences between hypervisors of Hyper-V an ESX, which outlines the arguments in much more detail.

  1. anonymuos 14 years ago

    I’m waiting for the day (probably never) when Microsoft releases a free standalone Hyper-V with OOTB locally managed admin GUI.

  2. What about Hyper-V Server? Its management console is not a GUI in the strict sense, but it does the job. A real GUI would just increase the attack surface.

  3. Ted Tyree 14 years ago

    The article is well written, but I feel the exact opposite. That for our data center (small compared to mainstream companies) the value is in the VMWare solution BECAUSE they do the work for us in getting the drivers to work with the VM hypervisor and abstract all of that from the Virtual Machine. Well worth a small 5% performance hit (if even that much) since it keeps the resulting image from being hardware specific. We have no guaruntee that the system we are going to ‘recover’ with in the face of a disaster is going to be similar hardware. The beauty and simplicity of a truly virtual machine completely abstracted from the hardware layer is exactly what we are looking for.

    Thanks for listening. Thanks for th article.

    -Ted Tyree

    • Marcuscassius 6 years ago

      I would tend to agree. Drivers have always been at issue with Winodws, even before hypervisors existed. The nice thing about VMWaare is that the drivers they use work….and work well.  I’ve had very few failures on ESX, unlike Windows, which seems to need a reboot every month, whether there was a change or not. I have had my eye on HyperV for a decade, and will continue to.  There introduction of containers in 2016 is  exciting.  I’ll be looking at the security for the new deployment. Keeping my fingers crossed.


  4. mark 13 years ago

    could you post me a link to the article. why can’t i find this article by Greg shields?

  5. Mark, the article is no longer available because Greg gave up his blog.

  6. vinyl 12 years ago

    even though Hyper-V supports more devices because it relies on Windows devices drivers, It really need Vcenter Server to manage ESX servers. It really dependent on third party like VMware.

    VMware will lead the world with Virtualization. MS is night mare 🙁

  7. Josh 11 years ago

    Are you seriously suggesting that hyper-v based in windows is less crash prone vmware esxi which is lightweight, purpose built, and fit for purpose?

    That must be some strong koolaid you’ve been drinking (no offense, but that assertion is nonsensical. Even windows sysadmins admin that windows is not an os built for uptime)

  8. Josh, the days where Windows was less “crash prone” than Linux are long gone. Besides, this post was about the hypervisor and you can run Hyper-V without Windows.

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