vmwareThe article today in our “VMware or Microsoft?” series is about the Guest Operating System support differences between VMware and Microsoft.

I am a technologist, who happens to work for for Microsoft (a leading provider of software, services, and now devices). With that disclaimer out of the way, let me state for the record, I try to  make fair apples to apples comparisons of the technology I evaluate. As a matter of fact, I think VMware ESX is a great product. I also think Hyper-v is a great product.

It irks me when any company, including Microsoft, puts out ridiculous marketing about a product. I know that companies are going to put there best spin on things but sometimes marketing goes too far. One of the reasons my group choose to do this blog series on VMware or Microsoft is because of this type of marketing. Here is a perfect example in this PDF that compares vSphere 5 vs. Hyper-V 3 (Beta). Wow, from that marketing it is obvious Hyper-v really sucks! What a misleading piece of “propaganda”. They could have made two more things green so it wasn’t so obvious.

I am not going to address the whole document today, I will just focus in on one of the statements. In my last series article, When it comes to hypervisors does size really matter?, I  addressed the claim that ESXi has a smaller attack surface (and is there for more secure and easier to patch). In this article I will take a look at the guest Operating Support claim that VMware Supports the Largest Number of Guest Operating Systems. This seems like a pretty straight forward fact but the details are a bit more muddy.

What is support? That all depends on how you define “is”

Support at Microsoft:
At Microsoft, when something is supported it means more than just we will take your phone call. Most supported scenarios need to be tested by the product group before the product is even allowed to ship. For unsupported scenarios we still do what we call “best effort support”. Which means we will take your call and try to help you get it working even though it isn’t a fully supported scenario. Heck, for a customer with a support agreement where you are paying by the minute, we will put in as much time as you want us to.  Winking smile For Hyper-v Guest OSs, support means that we have tested the OS and there are para-virtualization drivers for the OS. A lot of operating systems including DOS will run just fine in a Hyper-v but are still considered unsupported.

Support at VMware:
At VMware supported OS’s go into one of six categories. I pulled this from the VMware knowledge base article that you can view here.

Tech Preview

Operating system releases that have a Tech Preview level of support are planned for future support by VMware but are not certified for use as a guest operating system for one or more of these reasons:

  • The operating system vendor has not announced the general availability of the operating system release.
  • Not all blocking issues have been resolved by the operating system vendor.
  • One or more required enabling changes are not available in the form of a VMware product update or patch release.
  • Compatibility testing of a new OS update release is not complete.

Operating systems with this support level are fully supported by VMware. This includes technical support and engineering fixes.


The Legacy support level is between Supported and Deprecated. These guest operating systems are typically no longer supported by the original vendor. As a result, VMware’s ability to support this guest operating system is reduced.

VMware does not implement support for most newer VMware features and functions on operating system releases that are classified under this support level.


Prior to terminating support for operating system releases, VMware announces that the support for selected operating system releases has been deprecated in the product release notes and the VMware Compatibility Guide shows the support level for these releases as Deprecated.

A Deprecated operating system release is still supported by VMware and still receives technical support and engineering fixes (similar to Legacy) until it moves to the Terminated support level.


VMware does not provide support for operating system releases with terminated support.

Operating system releases with terminated support do not appear in the search results in the

Unsupported VMware does not provide support for operating system releases with Unsupported support level. This includes technical support and engineering fixes.

To find out if a guest OS is supported you can use this tool here: VMware Compatibility Guide. I used this tool to look up MSDOS 6.22 which was listed as supported by VMware and not by Microsoft. MSDOS 6.22 is listed in the Depreciated category and not the supported category. So does that count as supported? I looked up other OSs with the tool and noticed that even OSs in the supported category often have different things listed as unsupported. Many don’t support paravirtualization and hot Add of Memory or CPU. Under the fully supported category you have various levels of support. It may not even have VMware tools to install, so is it really supported better than “best effort support”? I guess it is better than best effort support but I don’t know if it is fully supported. Have all the supported OSs been tested before this version of ESXi shipped? I don’t know. Anyone, anyone, Bueller? It would be an impressive test matrix if they did. It would also be hard to ship a product if they required it to ship.


VMware’s comparison is not an apples to apples comparison. I feel their premise is true – VMware does have more supported OSs for ESXi than Microsoft does for Hyper-v; however, it is not the list that their marketing group put out. Also, just because an OS is in their supported column doesn’t mean that it is a first class citizen in their Hypervisor. Make sure to look up the OS that you want to use to see what things may or may not work.

The whole idea of choosing your virtualization platform based on how many OSs the vendor claims to support is pretty “silly”. The best way to pick your virtualization platform is to choose what works best for you and your workloads. For example, if you want to run Solaris 11 as a virtual machine in production then ESXi is the right choice because it is supported on ESXi and is not in Hyper-v. If you want to virtualize your Windows Small Business Server then Hyper-v is the way to go.

If you want to run the versions of  SUSE, CentOS, Red Hat, Ubuntu, Oracle Linux, or Windows that are supported on both; then take a look at both Hyper-v and ESXi. Do a real comparison and see how well does your actual workload performs in Hyper-v vs ESXi. Lab it up and let us know your experience in the comments! The price of Hyper-v sure is right. Hyper-v is included in Windows Server and we have a fully functional version called Hyper-v Server which is completely free. 

If you want to try our Free Hyper-v Server 2012 – download it here: http://www.microsoft.com/click/services/Redirect2.ashx?CR_CC=200256658

You can also get the Hyper-v Server 2012R2 preview here: