Why using a bare metal client hypervisor on a Mac makes no sense

Apple supports running Mac OS X 10.7 Lion in a client hypervisor VM on Mac hardware, but is there any value in virtualizing the Mac OS with Type-1 products such as XenClient?

A few years ago, Citrix created a huge amount of buzz by demonstrating a prototype of XenClient running on a MacBook Pro. Ever since the demo, people have been asking Citrix when XenClient will be released for Mac. But my question is, "Why would anyone want that?"

To understand why this doesn't make sense, let's take a step back. You probably know that there are two types of hypervisors, called Type 1 and Type 2. In the x86 world, the Type 2 hypervisors came out first. These are software programs that let you run virtual machines on top of an existing operating system (OS). Examples include VMware Workstation, VMware Fusion, Microsoft Virtual PC, Parallels Desktop and Windows XP Mode.

When most of us started using these 10 years ago, we thought, "Wow, these are cool for us IT Pros. But there's no way I’m giving this to an end user. It would be too confusing!"

And we IT Pros had other complaints about Type 2 client hypervisors, including the fact that they were clunky, slow and generally not a good user experience.

Then a few years ago, vendors started to release Type 1 bare metal client hypervisors. Unlike their Type 2 siblings, Type 1 hypervisors "replace" the local OS with a hypervisor. So, instead of installing Windows -- then VMware Workstation -- then running a second copy of Windows on top of that, you can install a Type 1 bare metal client hypervisor and run your two virtual machines (VMs) side by side.

This is great for performance, because since the OS is purpose-built as a hypervisor, it only has one job: to make those VMs run well! The user experience is better, too, since one OS doesn't have to run on top of the other, and administrators typically like Type 1 environments since they can be more secure. (The user can't infect/pollute/break the hypervisor.)

While client hypervisors haven't reached critical mass yet, Type-1 products like Virtual Computer NxTop and Citrix XenClient are steadily gaining popularity.

So what's this all have to do with the Mac?

First of all, if a user wants to run VMs on the Mac, we can already do that today with VMware Fusion, Parallels Desktop for Mac or the open source (and free) Virtual Box.

These solutions have been available for years and most people use them to run a Windows guest VM on top of the native Mac OS X.

Second, with last month's release of Mac OS X 10.7 Lion, Apple has officially decided that it's OK to run the Mac OS in a virtual machine as long as the host hardware is made by Apple. This means that you can use those aforementioned Type 2 hypervisor products to run a Mac OS X virtual machine on a Mac laptop.

It's also important to keep in mind that Mac laptops have been able to run Windows natively for several years. In fact, there are many Mac users who simply use the Mac hardware, but the first thing they do when they get a new Mac is erase the hard drive and install Windows natively on it -- they don't use the Mac OS at all.

Previously, these users would not have been able to run the Mac OS in a VM. However, with the licensing changes for Mac OS 10.7 Lion, it's now possible to run a Mac OS VM even if it's running on a Windows host. (Again, the catch is that the hardware has to be made by Apple.)

The question is, of course, why would anyone want to run the Mac OS in a VM? To understand this, you have to look at why people run the Mac OS in the first place. If a user believes that Mac offers a better end-to-end user experience, that user certainly isn't going to want to run the Mac OS in a VM. And if the user believes that Mac OS is better for the creative things like video editing, graphic design and Angry Birds, then the user isn't going to want to run the Mac OS in a VM.

From the admin's perspective, one of the reasons for deploying an OS in a VM is for simplified image management and deployment. But the Mac OS, by definition, can only run on Apple hardware. And there's already only a single image that works on all Apple hardware. So, the admin doesn't need to run the Mac OS in a VM in order to simplify image management and deployment because it's already simplified.

So, if you think about these things, you realize that the key reasons customers typically run Windows in a VM don't apply to the Mac OS. (The Mac OS even has built-in encryption annd backup.) In fact, the only reason that most people run the Mac OS in a VM -- at least today -- is so they can run side-by-side versions of non-compatible applications (like Final Cut 7 and Final Cut X), and those users will certainly want to run the host Mac OS on bare metal.

When it comes down to it, while Citrix XenClient running on a Mac was a cool demo that created a lot of buzz, it's not something that is actually needed. Users who choose to use Macs need the bare metal performance of a Mac OS installed locally. And users who need to run Windows apps on a Mac already have plenty of options with the Type 2 hypervisors.

So, even though Mac OS 10.7 Lion's licensing specifically allows it to be used in a VM, I wouldn't expect Type 1 client hypervisors around this anytime soon.

Read more from Brian Madden

ABOUT THE AUTHOR:
Brian Madden is an independent industry analyst and blogger, known throughout the world as an opinionated, supertechnical desktop virtualization expert. He has written several books and more than 1,000 articles about desktop and application virtualization. Madden's blog, BrianMadden.com, receives millions of visitors per year and is a leading source for conversation, debate and discourse about the application and desktop virtualization industry. He is also the creator of BriForum, the premier independent application delivery technical conference.

This was first published in August 2011

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