Backup-and-Restore: Changes to the contents of a VHD (such as infection by a virus, or accidental deletion of critical files) are easily undone.
As an example, software engineering organizations that need a specific set of tools for a particular project could simply 'pull' the appropriately-configured VHD from a network location.
Ease of deployment: IT organizations can deploy standardized, 'pre-built' configurations on a single VHD.
Significant benefits result from the ability to boot a physical computer from a virtual hard drive:
Linked to a hard disk (aka pass-through): a file that contains a link to a physical hard drive or partition of a physical hard drive.
Different child images based on the same parent image also allow "cloning" of VHDs at least the globally unique identifier (GUID) must be different. Options are available to undo the changes to the VHD, or to merge them permanently into the VHD. The Differencing hard disk image format allows the concept of Undo Changes: when enabled, all changes to a hard drive contained within a VHD (the parent image) are stored in a separate file (the child image).
Differencing hard disk image: a set of modified blocks (maintained in a separate file referred to as the "child image") in comparison to a parent image.
Dynamic and differencing VHDs begin with a copy of the VHD footer (padded to 512 bytes), and for dynamic or differencing VHDs created by Microsoft products this results in a VHD-cookie string conectix at the beginning of the VHD file.
Dynamic hard disk image: a file that at any given time is as large as the actual data written to it, plus the size of the header and footer.
Fixed VHDs consist of a raw disk image followed by a VHD footer (512 or formerly 511 bytes).
Fixed hard disk image: a file that is allocated to the size of the virtual disk.
The following types of VHD formats are supported by Microsoft Virtual PC and Virtual Server: VHDs are implemented as files that reside on the native host file system. VHDX was added in Hyper-V in Windows Server 2012 to add larger storage capacity, data corruption protection, and optimizations to prevent performance degradation on large-sector physical disks.
Life-cycle management and provisioning (re).
Disk conversion (physical to virtual, and vice versa).
Moving files between a VHD and the host file system.
The ability to directly modify a virtual machine's hard disk from a host server supports many applications, including: This method enables developers to test software on different operating systems without the cost or hassle of installing a second hard disk or partitioning a single hard disk into multiple volumes. A Virtual Hard Disk allows multiple operating systems to reside on a single host machine.
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