First, Thank-you for the Feedback
I wanted to quickly say thanks to everyone who provided feedback on our most recent post comparing the installation and configuration of VMware ESXi versus Windows Server Hyper-V with Server Core — Microsoft’s recommended deployment option. You may not agree with all of the conclusions we presented, but we just couldn’t let Microsoft Exec Bob Muglia go unchallenged in claiming that Hyper-V is simply “The Windows You Know” and therefore an easier product to use than ESXi – it isn’t. But thank-you, as many of you had very insightful (inciteful?) comments and we got some good, healthy debate going. For a pretty fair Microsoft response, please refer to James O’Neil’s blog .
But “Apples to Oranges”?? They’re Both Hypervisors!
But there was one piece of feedback, stated in comments by a number of Microsoft employees readers, that puzzled me. Some people cried foul because they saw our evaluation of Hyper-V with Server Core and ESXi as somehow comparing apples to oranges – I guess that was because Windows Server Hyper-V with Server Core requires a full instance of a general purpose operating system as its parent partition and ESXi does not. The comments/bloggers suggested that a more fair comparison would be ESXi vs. Hyper-V Server 2008, since Hyper-V Server is supposedly Microsoft’s ‘thin’ hypervisor that doesn’t require Windows Server OS in the parent partition – as reported by Microsoft here. (Note: the MSFT blog linked there incorrectly states that ESXi has a Linux parent partition. That is untrue, ESXi has no parent partition.)
Well, regarding “Apples to Oranges” I am not going to dwell too much on that one, because in my opinion, ESXi and Hyper-V (all configurations) are both Hypervisors and are both aiming to serve the same purpose within a customer’s datacenter, so therefore the comparison is valid. And, to support that notion, Microsoft compares all versions of Hyper-V to ESX/ESXi in every one of its virtualization presentations, so I think they’re in agreement with us that it is a fair comparison. However, given that, if you want us to compare ESXi to Hyper-V Server, sure, now that the product is finally available, we can talk about that one too.
Hyper-V Server – Initial Thoughts
Ever since Microsoft first announced Hyper-V Server, almost a year ago, we’ve been speculating as to what it would look like. It was billed as “standalone”, but until right before its release, Microsoft provided no technical details, so we were all left in the dark. Existing Hyper-V versions were wholly dependent on Windows Server, so how “thin”, how “standalone” could it really be?
(Note: I am actually thinking that, at the time of Hyper-V server’s announcement, Microsoft itself didn’t know what the Hyper-V Server 2008 architecture would look like…)
Well, now that Hyper-V Server 2008 has finally been released – with very little fanfare considering its initial push from Microsoft – we were able to perform a preliminary evaluation. There were two things we were initially interested in: 1) How the Hyper-V Server deployment/configuration processes compare to ESXi – gotta answer our critics, and 2) How Hyper-V Server architecture compares to ESXi – is it a more “apples to apples” comparison, or does Hyper-V Server contain Windows Server OS and is it therefore subject to all the patches, updates, vulnerabilities of the other configurations of Hyper-V?
We’ll save tackling the first issue — comparing the install/configure processes – for another blog post. While our initial eval tells me that the install/config process hasn’t improved with Hyper-V Server, it will still take a little time to undertake a complete analysis. But the second item – understanding what components of Windows Server the Hyper-V Server actually contains, how the architecture compares to ESXi, and what the benefits of Hyper-V Server actually are – we can start that discussion here.
Hyper-V Server is not “Windows-less” but is merely “Windows License-less”
Our initial finding is that Hyper-V Server is not “thin”; Hyper-V Server is still ultimately Windows. Hyper-V Server appears for the most part to be just Windows Server Hyper-V with Server Core where all other Server Core roles (except Hyper-V) have been disabled. Hyper-V Server has practically the same footprint as Windows Server Hyper-V with Server Core and is subject to the same patches, updates, attacks. It also appears to have the same restricting, indirect Windows-based driver model. In fact, it seems that the only advantage of Hyper-V Server is that one doesn’t have to buy a Windows Server license in order to deploy it – that’s it. Hyper-V Server is not “Windows-less”, but just “Windows License-less.”
Hyper-V Server also has some significant limitations that it seems to have inherited from the Standard Edition of Windows Server 2008. It can only support a maximum of 4 sockets per host, 32GB of physical memory per host, 31GB of virtual memory per VM, and requires a rip and replace upgrade to support features like Microsoft Clustering and Quick Migration. So it seems that Hyper-V Server is more of a starter kit, meant only for very basic use cases. In comparison, ESXi is a fully functional, production ready, enterprise offering. Actually, as 1) Both ESXi and Hyper-V Server are free and 2)Only free ESXi can easily be upgraded via license key to a production solution, why would anyone ever use Hyper-V Server? What’s the advantage?
Virtualization Needs
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Microsoft Hyper-V Server 2008
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VMware ESXi Free Hypervisor
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Small Disk Footprint
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No – 2500MB
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Yes – 32MB
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Large Host Memory Support
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No – 32GB
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Yes – 256GB
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Maximum Physical CPUs
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4
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32
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Maximum VM Memory
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31GB
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64GB
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Supported Guest OSs
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11
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30
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Memory Over-Commitment
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No
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Yes
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Production-proven
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No
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Yes
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Clustered File System
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No – NTFS
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Yes – VMFS
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Simple Upgrade Path
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No
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Yes, to full VI3 versions
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Hyper-V Server – An Overview of Our Installation Experience
For proof points supporting our above conclusions, following is a blow-by blow of Michael Hong’s experience installing Hyper-V Server:
I got my 936MB iso of Hyper-V Server downloaded. I burned it onto a CD and popped it into my brand new HP DL 360 and fired it up. After doing some recommended BIOS configurations and rebooting, I’m watching the boot sequence and getting a feeling of déjà vu. Did I just put in the wrong DVD? Because I swear this looks exactly like a full Windows Server 2008 or even a Server Core installation.

Wait…did that just say, “Installing Windows?” I thought this was Hyper-V Server that wasn’t supposed to be Windows! At this point I’m thinking, “Hey, maybe that’s not too bad. I can get a free copy of Windows without having to deal with any of their licensing nightmares.” Well let’s wait and see before I get too excited…
Hyper-V Server Disk Footprint is Similar to Hyper-V Server Core!
Okay, so after THREE more reboots I’m finally able to log in and start looking around. The first thing I check is Hyper-V Server’s disk footprint. After all, Microsoft states that one of its only three key benefits is a “small footprint.” So how “small” is it really? After plotting the numbers into my trusty byte convertor, Hyper-V Server is coming in around 2.5GB! (pagefile not included in size) WOW, that’s only a hundred megabytes less than a full-blown Windows Server Core installation! Perhaps it really just is a Windows Server Core Standard edition with one role enabled. Anyone else have any thoughts on this?

Also notice the number of files and directories. My basic install of Windows Server Core with Hyper-V enabled has:

In this install of Hyper-V Server there is actually more files and directories:

Next, let’s take a look at patching. Option number 5 in the dos-like Hyper-V Configuration menu shows an option for enabling Windows Update. Once set to automatic, it scanned for applicable patches. I didn’t expect to see any new patches since Hyper-V Server was just released yesterday. Any new patches would probably arrive next patch Tuesday right? And since this is supposed to be a light, secure hypervisor, it probably wouldn’t need as many patches as a full blown OS right? The results may surprise you:

13 applicable patches, including 2 for Internet Explorer 7? This is looking more and more like the “Windows I Know.” What in Hyper-V Server actually relies on IE7? Hyper-V Server looks like it’s a full blown Windows OS. If that’s the case, I’m sure hackers will have a field day copying over few additional files and turning it into a full working copy of Windows Server Core.
Some other things to keep in mind:
· Server Core and Hyper-V Server have the same directory structures
· Server Core and Hyper-V Server have the same command line toolset
· Server Core Standard and Hyper-V both have the same 32GB of physical memory limit and up to 4 processors
· Server Core and Hyper-V Server have the same parent partition driver model
Is Hyper-V Server really Windows Server Core Standard with only the Hyper-V role enabled? If so, will it be vulnerable to the same threats as Windows? Those 13 patches are just the starting point. What about viruses? Windows Server Core is exposed to viruses and as a result, there are anti-virus products out there today that are certified on Server Core. What about the size of Hyper-V Server’s footprint? Being only 100MB smaller than Server Core still shows it still has a very large attack surface as compared to VMware ESXi.
In Sum
We feel that, in contrast to how it is being marketed, Hyper-V Server 2008 is not “standalone”, “thin”, or Operating System agnostic in the same manner as ESXi. Hyper-V Server is still very dependent on and subject to the limitations of Windows and therefore should not be considered an equal to ESXi. Also, given Hyper-V Server’s restrictions and lack of upgrade path, and given that ESXI is also free and has a simple upgrade path, I question what the viable use cases for Hyper-V Server really are. Give it a try yourself and let us know what you think. Better yet, download our free VMware ESXi and let us know how you feel it compares to Hyper-V Server.
Stay tuned for our comparison of the deployment and configuration processes for ESXi and Hyper-V Server.