What are the VHD files under the Win7 system and what are their types

the meaning of a VHD file

The VHD file format is a virtual machine hard disk, which can be compressed into a single file on the host machine's file system, including the system files required for virtual machine startup. In Windows7 we can easily create a VHD by following the wizard through Disk Manager, or you can quickly create a VHD with the DiskPart tool

Application of VHD: Virtual PC is a kind of Windows virtual machine, it can be fictitious various versions of Windows, a Windows should be installed on a hard disk partition, but virtual windows, it is impossible to separate a hard disk partition for it to install, So it starts the required system files are compressed into a VHD format file on the hard disk, the VHD format is also applied in Windows Vista Business, Enterprise and Ultimate version, you can perform a full system backup.

　　Two, different types of VHD files

1, linked hard disk VHD

Refers to the file itself pointing to a disk or a partition.

2, Fixed VHD

The fixed VHD file is assigned a virtual disk size that is the size of the virtual disk specified when the VHD was created, and does not change for the allocated size. For example, if you create a virtual hard disk size of 2 GB, you will create a file size of approximately 2 GB, where part of the space is used for the internal VHD structure. The size of the fixed VHD does not change as the data is written to the virtual hard disk.

3, scalable or dynamic VHD

The value is the same size as the data being written, and increases as the data is written to the maximum size, and the dynamic VHD upper limit is 2,040 GB. For example, files that support a 2 GB virtual hard disk are initially about 2 MB in size on the host filesystem. As you continue to write data to this virtual hard disk, the file will gradually increase until you reach the maximum capacity of 2GB.

4, the Difference VHD

The

is similar to a dynamic VHD but contains only the modified virtual disk blocks of the related parent virtual disks, the upper limit of the differential VHD is 2,040 GB, the differential VHD is linked to a specific parent VHD, called the child VHD, the parent VHD file is read-only, all modifications are made to the child VHD, and the parent VHD's V The HD file type can be any of these three VHD types, including another differential VHD, and multiple child VHD files can form a chain of differences.