The buzz about Hyper-V, Microsoft's entry into the world of serious server virtualization, has been building for quite some time. This past week at Microsoft's mammoth North America TechEd 2008 conference, there was a focus on what Hyper-V (in Server 2008) was really all about and how it compares with VMware's ESX Server.

Many IT admins are familiar with the concept of a virtual system that resides on top of a host OS. Often times, I run several VM servers and workstation systems off one machine for testing and screen-casting purposes, with added RAM being the key to maintaining some level of performance. VMs are RAM hungry more than anything else. The difference between lower-end virtualization offerings and high-end variants such as ESX and Hyper-V is that the host OS is no longer the go-between for the VM Server and the hardware. In both cases, a hypervisor is used, allowing the virtual OS to access the hardware directly (or what they call bare-metal performance).

What Hyper-V does a little differently from ESX Server is that it keeps the drivers out of the hypervisor and allows the VM systems to retain them all above -- whereas ESX places drivers within the hypervisor. Thus, the hypervisor for Hyper-V is significantly smaller than ESX Server 3.5, which allows for less code involved in the scheduling and sharing of hardware resources.

Some of the differences between the two products are minimal or nonexistent. For example, they both support four virtual CPUs, as well as 64GB of maximum RAM per VM.

But there are significant differences that can be real deal-breakers. For one thing, only the more mature ESX Server has the capability of using a 32-bit OS as the host. The same is true of sharing memory between VMs; Hyper-V can't do it.

However, pricing of Hyper-V is significantly lower than ESX because the Hyper-V role is directly part of Server 2008. For a more detailed examination of the advantages and disadvantages of each, see Michael Otey's coverage over at Windows IT Pro.

One thing I found interesting was that you begin the process of installing Hyper-V by installing Windows Server 2008 (64-bit edition and, logically, one that supports Hyper-V). You install the hypervisor with a single click as a "role" (which fits nicely with the fact that roles are being utilized heavily in the new vernacular of Server 2008 configuration). You reboot the system -- and according to Dan Stoltz, one of the program managers for virtualization with Microsoft, it's like the existing OS is lifted up and the hypervisor layer gets placed beneath it. Now that OS is called the parent, and future VM systems are called child systems.

There is a Hyper-V manager on each server within the parent role for managing your VMs and your Hyper-V servers. But for more extensive management, Microsoft offers System Center Virtual Machine Manager. (Note: System Center tools were also heavily demonstrated at TechEd as the performance and event monitoring product that Microsoft will push going forward.)

The final release of Hyper-V is due out in late August, but you can download the release candidate to see for yourself if it meets the hype.

Now, keep in mind that Hyper-V and ESX Server are only two of the virtualization options available to enterprises. There is, for example, Virtual Iron and others. What virtualization software are you using or do you plan to use within your enterprise? I'd like to know!