Product Documentation

VHD Chain of Differencing Disks

Sep 28, 2016

Versioning simplifies vDisk update and management tasks, providing a more flexible and robust approach to managing vDisks.

A vDisk consists of a VHD base image file, any associated side-car files, and if applicable, a chain of referenced VHD differencing disks. Differencing disks are created to capture the changes made to the base disk image, leaving the original base disk unchanged. Each differencing disk that is associated with a base disk represents a different version.

The following illustrates the file naming convention used and the relationship between a a base disk and all versions referencing that base disk.

VHD Chain

Note: vDisk versions are created and managed using the vDisk Versions dialog and by performing common vDisk versioning tasks.
Each time a vDisk is put into Maintenance Mode a new version of the VHD differencing disk is created and the file name is numerically incremented, as captured in the table that follows.
  VHD Filename Properties Filename Lock File Filename
Base Image win7dev.vhd win7dev.pvp win7dev.lok
Version 1 win7dev.1.vhd win7dev.1.pvp win7dev.1.lok
Version 2 win7dev.2.vhd win7dev.2.pvp win7dev.2.lok
... ... ... ...
Version N win7dev.N.vhd win7dev.N.pvp win7dev.N.lok

For information on merging VHD files, refer to merging VHD files.