Virtual Hard Disk (VHD)
The Virtual Hard Disk (VHD) commonly uses the .vhd extension.
This format is used to store virtual disk images by:
- Microsoft Virtual PC
- Microsoft Virtual Server
- Microsoft Hyper-V Server
There are multiple types of Virtual Hard Disk (VHD) images:
- Fixed-size hard disk image; the image contains all data
- Dynamic-size (or sparse) hard disk image; the image contains used data only
- Differential (or differencing, or delta) hard disk image; the image contains changes relative to its parent image
Hyper-V has functionality to create snapshots.
These snapshots are stored in Snapshot Differencing Disk (AVHD) files which commonly uses the .avhd extension.
The snapshot can be interdependent on one-another, because they are differential images of the previous snapshot.
- VHD (file format), by Wikipedia
- Virtual Hard Disk Image Format Specification, by Microsoft, October 2006
- Virtual Hard Disk (VHD) image format, by the libvhdi project, September 2012