Roman Smitko, 123RF

Managing VHD devices

Disk World

Article from ADMIN 03/2011

By Thomas Drilling

Windows 7 implements virtual hard disks as VHD containers that offer many advantages over physical drives. We take a closer look.

Since it was released in 2009, Windows 7 has received fairly good marks – it's certainly proven superior to the unfortunate Vista. One notable new feature is the hard disk management program's ability to handle virtual hard disks on Windows 7.

Virtual hard disks (VHDs) traditionally use the VHD format in the Windows world and are simply container files on the host filesystem. The VHD format is also used by Microsoft's Virtual PC and the Hyper-V component of Windows Server 2008, which means you can use a VHD file that you set up on Windows 7 in Virtual PC or Hyper-V. The option of booting from a virtual hard disk seems even more interesting, but Microsoft doesn't give you that for free.

Utility Value

The advantage of VHD files at the Windows 7 system level is that you can easily back up and manage virtual hard disks because they are simply files on the host system. And, compared with physical hard disks or partitions, there are virtually no disadvantages; the read and write performance is typically just a couple of notches down from that of physical access.

Unfortunately, the sleep features and Microsoft's BitLocker hard disk encryption do not work with VHD files. The biggest benefit of VHD files is that you can actually boot Windows 7 from a VHD drive, which gives administrators intriguing options for enterprise-wide deployment of Windows 7 installations.

Windows 7 can be configured to boot from VHD files only, so you don't even need to install an operating system on your desktop systems.

On paper, Microsoft seems to have integrated an interesting technology with Windows 7 and its VHD drives. If you need to experiment with operating systems as an administrator, you will need either a full-fledged virtualization server on a hypervisor basis, such as VMware ESX or Citrix XenServer, or a large number of disks and some partitioning

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