What is the VHD file under Win7 system and what type is it?

First, the meaning of VHD file

The VHD file format is a virtual machine hard disk, which can be compressed into a single The file is stored on the file system of the host machine, mainly including the system files required for the virtual machine to start. In Windows 7, we can easily create a VHD through the disk manager according to the wizard, or create a VHD quickly through the diskpart tool

VHD application: Virtual PC is a kind of windows virtual machine, it can virtualize various versions of windows, a windows should be installed on a hard disk partition, but virtual windows, it is impossible to draw a hard disk partition to install it separately. So the system files needed to boot are compressed into a VHD format and placed on the hard disk. The VHD format is also applied in the Business, Enterprise and Ultimate version of Windows Vista for full system backup.

Second, different types of VHD files

1, linked hard disk VHD

refers to the file itself points to a disk or a partition.

2, Fixed VHD

The fixed virtual disk size of the fixed VHD file is the virtual disk size specified when the VHD was created, and will not change the allocated size. For example, if you create a virtual hard disk with a size of 2 GB, the system will create a file with a size of about 2 GB, some of which is used for the internal VHD structure. The size of a fixed VHD does not change as data is written to the virtual hard disk.

3, scalable or dynamic VHD

It is worth that the size of the data is the same as the size of the data written, and increases with the data until the upper limit is reached. The upper limit of the dynamic VHD is 2,040. GB. For example, a file that supports a 2 GB virtual hard disk is initially about 2 MB in the host file system. As data is continuously written to this virtual hard disk, the file will gradually increase until it reaches the 2GB capacity limit.

4, Difference VHD

Similar to dynamic VHD, but only the modified virtual disk block containing the relevant parent virtual disk, the upper limit of the difference VHD is 2,040 GB, and the difference VHD is linked to the specific The parent VHD, called the child VHD, the parent VHD file is a read-only file, all modifications are made for the child VHD, and the parent VHD's VHD file type can be any of these three VHD types, including the other Differential VHD, multiple sub-VHD files can form a differential chain.