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Scoping out the subtle differences between Hyper-V and VMware

Hyper-V and VMware both provide hypervisor virtualization. But while the two are similar, there are subtle differences.

Just as users run both Windows and Unix environments in the same shop, there are reasons to run different virtual environments, even if they do essentially the same thing.

Hyper-V is built into Windows Server 2008 and Windows Server 2008 R2, making it easy to deploy quickly on existing Windows installations. It’s also included in the price of the operating system, making it ideal for situations where added licensing isn’t warranted. It also supports any hardware that is certified for Windows Server 2008 or 2008 R2. Drivers, adapter and network adapters all work if they include Windows-certified drivers. This provides more leverage to use existing hardware without worrying about some of VMware’s narrower list of approved hardware.

Hyper-V and VMware are similar in that they are both hypervisors operating at low levels with the hardware. It would be a mistake to think Hyper-V is just the latest version of Virtual PC, the virtualization software that runs from inside Windows. Hyper-V comes with the same kind of optimizations that VMware has including optimized drivers, enhanced storage access and security features. The basic concepts of ESX and ESXi all apply, meaning one can count on having virtual switching, access to SAN, as well as iSCSI storage and the ability to control the virtual machines.

But it is the differences that matter the most to VMware administrators.

The first noticeable difference is the hypervisor seems to run inside Windows, but this is just the parent partition. The hypervisor is actually operating underneath the operating system. The way the management interface is accessed is also different.

Like VMWare, Hyper-V can manage the console of virtual machines, although users do so using the Hyper-V Manager instead of the VI client. Admins can launch this on the parent partition if they are running a full-blown Windows installation, or do it remotely after installing the tools on the workstation. There is also a version of Hyper-V Server that is essentially a Windows Server Core installation with Hyper-V installed and like VMware ESZi, its free to download and use.

VMware administrators are well aware of the need to have compatible hardware. This is true of Hyper-V as well, although Hyper-V is compatible with any hardware that is certified to work with Windows Server. When addressing that hardware, Hyper-V’s version of VM Tools is called Integration Services. Just as in VMware, Hyper-V has a menu option to install the Integration Services as a mounted CD in the virtual machine. As with any virtualization system, admins should ensure this is done to get the maximum performance out of the drivers. The supported operating systems for Integration Services is more narrow than that of VMware, so check compatibility before clicking install.

The initial hard drive is installed as an IDE drive in Hyper-V. This actually takes care of some initial compatibility issues with some operating systems since VMware makes SCSI disks available to its virtual machines. Hyper-V R2 makes the SCSI controller a standard feature, which brings the added benefit of hot swapping. Another popular option in VMware is thin provisioning, which allows the disk to be presented to the guest as a certain size, while physically only taking the space that is actually used. In Hyper-V, these are Dynamic Disks and users will be asked if they want to set this up when creating a new virtual machine.

Pass Through Disks support permits access to a LUN without configuring it as a volume, which makes shared storage for failover clustering possible. Hyper-V users can then take advantage of Live Migration and VMware users can take advantage of VMotion. To set up Hyper-V for failover, it is important to review Clustered Shared Volumes, which enables features similar to the VMFS clustered file system.

There are a few additional tips to help admins maintain their sanity. VMware virtual machines issue a Control-Alt-Delete with the key combination Control-Alt-Insert. When working with Hyper-V, the same combination as a Remote Desktop Protocol session is entered with a Control-Alt-End. Also, VHDs are the format for disk drive files, so don’t go looking for a VMDK file in Hyper-V.

There are plenty of ways Hyper-V and VMware differ, but overall it’s all hypervisor virtualization and that means the concepts from one platform apply to the other.

Eric Beehler has been working in the IT industry since the mid-90's, and has been playing with computer technology well before that. He currently provides consulting and training through his co-ownership in Consortio Services, LLC.

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