VHD is an abbreviation of Virtual Hard Disk. These are file formats that represent a virtual hard disk drive. The data found on a physical hard disk drive may be involved in it just like the partitions of the hard disk and file system which comprises folders.
For a virtual machine, the VHD files are considered hard disks. In the modern Windows versions, these are built-in. This specific virtual type of hard disk provides the facility for different operating systems to reside on the common host machine. It provides a great chance for the developers to test the software on several OSs without doing the process of installation of another hard disk. There are many advantages of using this file format of VHD files as these provide many features.
Connectix developed this file format as a virtual PC product for their usage. In 2003 Microsoft acquired Connectix and launched other versions of this format such as VHDx along with the better features and functionalities which had been missing in the first version. In 2012 the VHDx was added into Windows. It was added into Windows to add more capacity of storage, protection against data corruption, optimization to prevent the degradation of performance. These features were added for physical disks with large sectors.
VHD File Format
A host file system is accessed to reside the VHD files on it. These have features of the fixed image of the guard disk which allows the user to access a file that is allocated the size of a specific virtual disk. The files can modify the hard disk of a virtual machine.
These VHD files can be exchanged easily from the virtual hard disk to the file system of the host. This format also has the capability of backup and restores and antivirus security. The VHD files can support specific formats like a Fixed hard disk image, Differencing hard disk image, and Dynamic hard disk image.