One of the much-touted new features in Windows 7 and Windows Server 2008 R2 is VHD Boot, which lets you start the OS from a Virtual Hard Disk (VHD). Microsoft recommends it as a more flexible alternative to a traditional multi-boot configuration, because you can avoid the static partitioning of your hard disk.
Another advertised advantage of the new feature is ease of portability between physical and virtual, theoretically, you should be able to run the contents of a Virtual Machine on bare metal. But don't expect, it's going to be easy. Chances are that your computer will hang when starting from a VHD, you created using Virtual PC or Hyper-V. That's because the virtual hardware may differ from the physical one. Additionally, paravirtualized drivers used to accelerate Windows in a VM pose a problem when booting an existing VHD physically. In many cases you will end up sysprep-ing your VHD before porting it over to the physical /virtual world.
But back to VHD Boot as a more flexible way to install multiple OS on a PC. If you need a test or demo environment, how does VHD Boot stack up against alternatives most people use in this case? Since the advent of Desktop Virtualization, partitioning a hard disk and using a boot manager to switch between operating systems may not be your favorite choice. But, in many cases, it is still superior to VHD Boot. The implementation of the new feature can't live up to the high expectations. The following feature comparison shows that you are probably better off using a solution like VMware Workstation, Virtual Box or Virtual PC instead of VHD Boot.
German readers might want to read the original posting on windowspro.de
|VHD Boot||Multi-Boot||Desktop Virtualization|
|Supported Operating Systems||Windows 7 Ultimate/Enterprise,|
Windows Server 2008 R2
|All (as long as they are compatible with the boot manager)||All popular OS|
|Can use the OS without limitations?||No. No Hibernate, no encrypted or compressed volumes, no Bitlocker.||Yes||Some restrictions possible, e.g. resource conflicts between host and guest system|
|At file system level. VHDs can be mounted from Windows 7||At file system level, granted that the active OS can read the file systems in other partitions.||If the virtualization layer offers integration components for the guest OS, integration at file system level and copy & paste between host and guest.|
|Flexible usage of disk space||In theory, yes (when booting from a dynamic VHD). Microsoft recommends fixed VHDs for VHD Boot.||No, rigid partitioning necessary.||Yes, dynamically growing virtual disks are default|
|Portability||Limited (also between virtual und physical).||None.||Limited, depending on hypervisor and hardware|
|Rollback||Limited. Creating a differencing VHD with diskpart only, manual reset of changes.||No.||Depending on the hypervisor, you can undo changes step by step or create snapshots.|
|Installation||Setup form Windows installation medium not possible. Instead deployment with WAIK Tools (ImageX), wim2vhd or Disk2VHD||Windows Setup, Boot Manager may cause difficulties||Windows Setup (if VM can boot from DVD)|
|Update to newer version of Windows not possible. Patches can be applied offline using the Offline Virtual Machine Servicing Tool. It requires System Center Virtual Machine Manager (SCVVM).||Windows Update possible. After a longer period of inactivity, an installation may become a security risk due to missing patches.||Upgrade of Windows possible. Same patch problem as Multi-Boot configuration.|
|Performance||Nearly identical with native installation||No limitations||Some performance penalty due to virtualization overhead|
|Tools support, usability||Inconsistent and awkward.||Depending on Boot Manager and installed operating systems.||Mature tools in most cases, depending on the hypervisor|
|Suitable for production environments?||Yes, but critical data should be stored outside the VHD.||Primarily for test environments.||Yes. Without Med-V or Unity-Mode (VMware) no seemless integration of guest apps => not appropriate for office users.|