Making sense of four client hypervisor vendors: Virtual Computer, Neocleus, Citrix & VMware

We've been talking about client hypervisors quite a bit over the past eight months or so. Right now there are four vendors who've announced products in this space, and frankly it can be kind of easy to get them confused and remember who's doing what.

We’ve been talking about client hypervisors quite a bit over the past eight months or so. Right now there are four vendors who’ve announced products in this space, and frankly it can be kind of easy to get them confused and remember who’s doing what. So in this article we’ll take a lot at each of the four vendors (as well as an open source project) and outline what we know about them so far and what we understand their plans to be moving forward.

Our four vendors, in random order, are:

As a fifth bonus offering, we’ll also take a quick look at the open source Xen Client Initiative.

Before we get started, I’d like to quickly share a comment that Neocleus’ Bill Corrigan made to me yesterday. He said (and I’m paraphrasing this), “Brian, you keep on saying the client hypervisor market is crowded. But there are only four players in it and over a billion PCs in the world. I think there’s enough room for us all.”

Good point, especially if you consider that these four vendors don’t necessarily compete with each other. True, they’re all orbiting around the general concept of the client hypervisor, but they each have their own goals and ideas for where they want to take it and why they think client hypervisors are important.

Let’s look at them one-by-one.

Virtual Computer NxTop

Virtual Computer is a Boston-area start-up company with a product called “NxTop.” NxTop combines a Xen-based client hypervisor with a back-end management system to create a PC lifecycle management solution. In other words, Virtual Computer isn’t competing against VDI, they’re competing against the Altiris and SMS / System Center products of the world. Their general reasoning is that putting a hypervisor on a laptop allows them to manage Windows from the outside, so they can push down images and delta patches, do encryption, remotely kill machines, etc., all via a single agent running in their own Dom 0.

Virtual Computer’s solution is a complete turn-key solution, so when you buy it you get the hypervisor, the disk image creation tools, the on-demand master disk creation capabilities, the remote distribution and patching capabilities, security, online and automatic backup, and everything else you need to make it work. As such, they’re really targeting small and medium businesses since larger companies probably already have in-house solutions for a lot of the features that Virtual Computer offers.

Right now the hypervisor / client piece is a destructive install, in that it can only be installed by blowing away everything on the client’s disk. They’re working on more interesting ways of doing that in the future though.

Back in January, Citrix invested in Virtual Computer. Both companies claim that working together will let them create a better hypervisor product, and a better client hypervisor will help everyone. To that end, Virtual Computer does NOT view their hypervisor as a competitive piece of intellectual property, and they talk of giving back to the open source community. So far that’s just talk though, and they don’t seem to have released or contributed any open source code. (Although to be fair, they’re also not shipping a product yet.) [UPDATE: Virtual Computer has made some of their changes available via]

Past Virtual Computer coverage on

Virtual Computer video demos

Virtual Computer product status

  • Available now, but still in quasi-test mode as it's only for environments up to 25 users.

Neocleus Neosphere

Neocleus is the other start-up company in this space. They were the first company to publicly launch a client hypervisor (just a few weeks ago), and now their “Neosphere” product has been officially released. Neocleus is an Israeli company, which means that while their user interface occasionally leaves you scratching your head, the security of their product is just ridiculously badass.

Unlike Virtual Computer, Neocleus is focusing 100% on the enterprise space. This means that they’re not trying to build a complete system. (Because, for example, enterprises probably already have software distribution methodologies and backup solutions and many of these things, and in their case, they just want a client hypervisor that can integrate with there existing stuff.

This is not to suggest that Neocleus doesn’t have a management console. (They do.) It just means that their console is focused on managing the hypervisor-specific aspects of the client.

Like Virtual Computer, Neocleus is basing their solution on the open source Xen hypervisor. They’re taking a bit of a different tack on implementation though, and focusing on achieving native performance in all VMs running on the client.

Everything about Neocleus is just well thought-out for the enterprise. Take the first-time distribution of the client, for example. Most enterprises already have laptops in the field (or users procure laptops that already have operating systems on them from the local Best Buy or whatever). Instead of forcing the user to wipe the hard drive to install the hypervisor, the Neocleus install package is a normal MSI that runs like any regular Windows app. Their client installs and the laptop reboots into the user’s normal OS, except now that OS is running in a VM! They leave the file system in place and just install their hypervisor underneath it! From there you can push down VMDK or VHD files to boot and run at the same time.

If you later decide that you don’t want a particular user using their hypervisor, you can even remove it in a non-destructive way and boot back to your copy of Windows running natively.

Past Neocleus coverage on

Neocleus video demos

Current Neocleus product status

  • Available now.

Citrix XenClient

Citrix announced their client hypervisor this past January as something called “Project Independence,” and at Synergy a few weeks ago they announced the official product name would be “XenClient.” Citrix also announced that XenClient would be free, but remember, there’s “free,” and then there’s “free.”

I have no doubt that the actual hypervisor called XenClient will be free. (In fact that might even end up being the same build that Virtual Computer uses, or perhaps the same build as the open source Xen Client.”)

At the end of the day though, Citrix doesn’t make money by giving things away for free. So much like the ICA client is free, it’s free because it’s used to connect to back-end Citrix servers that you pay for. For the case of XenClient, Citrix undoubtedly sees this as an extension to their XenDesktop product.

Another reason to make XenClient free is to try to get the momentum in the market behind a Xen-based solution. If Virtual Computer, Neocleus, and Citrix can convince everyone that a Xen-based client hypervisor is the way to go, and if notebook vendors buy into that standard instead of whatever VMware does, that could be very good for them.

Past Citrix XenClient coverage on

Citrix XenClient video demos

Current Citrix XenClient product status

  • They’ve demoed it publicly. Beta is not yet available. Product is scheduled to be released 2H09.

VMware Client Virtualization Platform (CVP)

From a philosophical standpoint, it’s important to remember that fundamentally, VMware is more about managing the VMs than managing the clients. So I almost get the feeling that with someone like Virtual Computer, the client hypervisor is the means to an end, while with VMware, the client hypervisor is the end. My sense is that VMware's initial push is going to be more about offline VDI--essentially taking what they already have in beta today and extending so it works without an underlying OS.

The main problem with CVP today is that we just don’t know about it. One line of thinking is that VMware is really far behind schedule and they’re delaying everything. The opposite viewpoint is that since VMware dominates the platform virtualization market, they can afford to just sit back and let the Xen-based folks make the first move. Then they can reveal their own hand after people provide some real world feedback on the competition.

Past VMware CVP coverage on

VMware CVP video demos

  • Umm… yeah. If they ever decide to show anyone this thing, we’ll let you know!

Current VMware CVP product status

  • A nice set of PowerPoints. No public demos. Not yet in beta. Scheduled to be released 2H09.

Open source Xen Client Initiative

Remember that the actual Xen hypervisor is open source. And the open source people creating this thing are also creating an open source version of the Xen hypervisor for laptops which is known as the “Xen Client Initiative” (or XCI). This is not to be confused with Citrix’s “XenClient” (no space). So “XenClient” is the commercial product, and “Xen Client” is the open source thing. I think.

Actually, when Citrix said the XenClient would be free, I wonder if that’s even going to be a Citrix product? Maybe Citrix and are actually talking about the same thing, and the free “XenClient” from Citrix will actually be the open source "Xen Client?"

Past Xen Client Initiative coverage on

  • None

Xen Client Initiative video demos

  • None (There’s a blog post on talking about Xen Client Initiative demos, but it links to the Citrix XenClient demo from iForum!?!)

Current Xen Client Initiative product status

The “cheat sheet” version of this article

So there you have it. Just to review:

  • Virtual Computer – Xen-based hypervisor, complete system, focus on SMBs, competing against PC lifecycle management vendors
  • Neocleus – Xen-based hypervisor, focusing on creating the right hypervisor for the enterprise, near-native performance in multiple VMs
  • Citrix – Xen-based hypervisor, really planning to extend their XenDesktop product
  • VMware – only vendor not using Xen, plans for this to be like “offline VDI,” so more of an extension of an existing VDI environment
  • Open Source Xen Client Initiative – Completely free, but hypervisor only. Could ultimately share some code with Citrix, Virtual Computer, and/or Neocleus

What do you think? Did I miss anything important from any of these vendors?

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Good article Brian.

If Neocleus does not do anything to manage inside the Hypervisor, then what Enterprise value to they really bring, apart from some niche security appliance? It seems to me, this just adds to costs, and goes against the benefits of changing the managment model (single image + apps + user), which the System Centers of the world are doing do little to address. The greatest pain point and costs in my view of Latops etc is mobile management due to seldom connectivity. Therefore to only have a strategy to manage the VM, leaves the complexity intact and offer limited benefit for the masses.

Seems like drivers is also going to be big deal on the client side. This is where hopefully a XenClient base for all vendors will help. I am sure this is where the like of Neoclues will try to optimize, but what's the value in a commodiy Hypervisor if Citrix is going to make it free anyway...

VMWare. Just because they dominate on the server side today, why would anybody pay them to build a client solution, I don't get their model in this space. Hopefully they'll do something smart here.

MS MS MS. The godfather. I wonder if they will ever bother with Hyper-V for the clients, or just buy their way in over time. Seems to me they are missing the boat here, or they just don't care about this space until it's proven.

In summary, my view is that the real value is in who manages inside the Hypervisor the best to reduce costs coupled with VM management. Also I know the focus of this article is Type 1, but Moka5 adds these features to Type 2 also, so I see no reason why they couldn't expand their awesome managment to Type 1 over time as well.



One important that I think you forgot to mention was teh hardware requirement to run these Hypervisors on. My understanding there is that VPro is required for Citrix and VMWare for now for sure. I', not sure if Virtual Computer requires VPro, or if like Neoclues can just run on a VT enabled machine. Would be curious to poll th community to get a sense of what % of their HW can handle these requirements, and if not a meaningful %, how far out do you expect a hardware refresh to take place vs. your last one.

Another side bar. If VDI can enable you to simply repurpose your exisiting PC's and extend their life without having to buy thin clients, what % of those would be viable for Type 1. I know only a tiny % of my PCs could do anything with a Type 1 Hypervisor thanks to VDI.............


@ appdetective,

Good point that exactly what I am thinking about the repurpose of existing PC by VDI against the client hypervisor requirement coz of the tiny %, but we do need offline feature for any type of endpoints.


Thanks for going a level deeper on the client hypervisor players, Brian.  A few comments from Virtual Computer HQ:

- At the end of March, we transitioned from beta to a paid launch program called NxTop Now!  Given that we were taking purchase orders from paying customers immediately upon launch of this program, I would argue that Virtual Computer was first to market with a true shipping product.  Of all of the vendors profiled, we appear to be the only one where there is a clear and definitive method of purchasing the product on the web site (

- While our ability to provide a turn-key solution allows us to scale down to the SMB, we have significant traction in the corporate and enterprise segments as well.  All of the capabilities we have to create, maintain, deploy, and perform one-to-many updates to virtual desktops through our management GUI are exposed through a rich set of APIs, allowing us to act as an extension of existing management infrastructure as well.

- In conjunction with our 1.0 release in March, we made all of open source enhancements available on our web site at (also linked from other areas of our web site).  No hoops to jump through whether you are a customer, friend, or potential competitor.



I agree with offline, but again the same applies. At least in my case, a small percentage of my fleet have VT let alone VPro, hence Type 2 makes more sense for me, with a killer mgmt stack that moves to Type 1 over time for the superior secuirty and performance as hardware is refreshed and people are comfortable putting it on their machines which is huge mental barrier to overcome in my opinion.



I would also like to get a better understanding of which vendors virtualize the driver set and which do not as well as the benefits and drawbacks of both approaches with regards to driver management in VDI.

From what I gather is this:

- Virtual Computer's NxTop virtualizes the driver set

- Neocleus NeoSphere does not virtualize the driver set

- Citrix's XenClient does not virtualize the driver set

- VMware's CVP is rumoured to virtualize the driver set

I keep getting confused because I had the impression if you do not virtualize the drivers you are still going to have to bake the "golden" OS with a ton drivers for all of your hardware much like what it is now for PVS. I thought Citrix was trying to get away from that? Maybe I was wrong.

And if you did virtualize the driver set it would be "a path to purgatory in hell" (Quoted from Citrix CTO Simon Crosby) and would not be ideal because you have to re-write all of the drivers for all possible hardware from all vendors.


@Doug Lane, thanks for the clarifications. I'm going to make a few updates to the article based on that. For the other vendors out there, feel free to post your thoughts to these comments as well.

@Everyone, for the question about drivers... great question! (And something I didn't think about. I don't know if I'll be able to dig into that for this article, but that can definitely be a future article.)



As you mention in your article about the open source Xen Client Initiative project:

"Early build is available now via (But this is a git repository and I can’t figure out how to find the actual code. A little help?)"

The early build available is currently being actively developed on and is for the open source development community to work with as a base. The community is busy adding patches to this build and is not something ready for users to try. When the community feels the build is stable and enough testing has been complete, an official release will be created by the community. I recommend that your readers wait until such a release before attempting to build and install this client hypervisor. This is similar to the current method that we release Xen server hypervisors (e.g. our new Xen 3.4 release).

As for my links to the Ian Pratt videos at Synergy, the hypervisor being shown is coming from the open source XCI project with some additional work by Citrix to ensure the success of the demonstration. I did not intend to cause confusion among your readers but merely to allow people working on the XCI project and prospects a chance to see the client hypervisor in action. Citrix will base their solution on the XCI project as will other vendors and I should have been clearer on that point.


Anyone notice the money trail here. Citrix has invested in Virtual Computer. And Intel has invested in Project Independence. Commitments are great, but when the someone actually put their hands in their pocket and pony's up some cash, then we know they're serious.


I suspect that most of your readers are enterprise guys, either on the vendor or customer side. I'm interested in this topic for different reasons.

Today, I'm an SMB owner and am struggling with my own notebook machine. I facing the prospect right now of having to rebuild my 1 1/2 year old Thinkpad because of mysterious BSOD issues in my XP install that will not be easily resolved. I know legions of others in my situation.

I'm in the technical business, and practice reasonably safe computing, including having good backup images of my machine, and daily backup of my data. Still, something happened recently that has created an unstable computing environment for me.

I've been readying myself for a potential leap to Ubuntu, and already am dual boot, and also have a virtualbox machine built with XP on it, but the fact my nicely tuned (previously) working XP system is not portable (e.g. to a new machine) will turn out to be a business problem for me (mostly in time necessary to transition if that occurs).

I wouldn't be spending too much thought on this, but not too long ago this same Thinkpad's screen shattered, which necessitated me thinking long and hard about a new machine (I eventually ebayed a replacement LCD), but again the thought of having to somehow reinstall everything (a total PITA for those in the Windows world), which I decided to not go through.

At the same time we were exploring helping a client who seemed like a good candidate for ESXi. Voila I thought, why not run this on my X61. I was soon reminded that this was not an option.

Is any of this ready for prime time for my situation? Yes I realize that I could build a very skinny install of Linux or even Windows, then run VMWare or VirtualBox on top of that, and achieve the same effect, but having a full blown OS first that then launches a virtualization app, that then launches an OS seems incredibly inefficient.

I would love some practical (e.g. can do this now) thoughts on client virutalization as it relates to my situation.

If I could work this out, I would take the 10 other folks within our enterprise and push them all down that road so that none of us will be caught with our pants down in the future.