Introduction to vhd mode

Most people first come into contact with VHD format files when using Virtual PC or Virtual Server. VHD is a virtual machine disk that exists in the form of a file.

Microsoft disclosed the full details of the VHD format file in 2005. The Virtual Hard Disk Image Format Specification can be downloaded from Microsoft's TechNet website.

This shows that Microsoft not only wants to apply VHD in the field of virtual machines, but also hopes that VHD can become a new disk format and carrier and gain more support in the industry.

Let's put aside the virtual machine and focus on the VHD file itself.

VHD is a virtual hard disk. Different from the platters, heads and tracks of a traditional hard disk, the carrier of a VHD hard disk is a VHD file on the file system.

If you read the technical standards of VHD files carefully, you will find that the standard defines many hard drive-specific terms such as Cylinder, Heads, and Sectors to simulate I/O operations on the hard drive.

Since VHD is a hard disk, it can be partitioned, formatted, read and written like a physical hard disk.

We can think of it this way, VHD is also a type of hard disk, just like hard disks of different specifications such as 2.5-inch, 3.5-inch, SCSI, SATA, IDE, etc. VHD is a hard disk in a file.