Which of the following statements is NOT correct about a differencing disk?

• A. Changes made to a VM hard disk apply only to the parent disk, with its differencing disk unaltered
• B. It can store different states of the parent disk
• C. It allows for reverting to a previous state of the virtual machine
• D. It is dependent on the parent disk for storage

Answer: (A)

A differencing disk is designed to work alongside a parent disk to provide flexibility in managing virtual machine states. The statement about changes made to a VM hard disk applying only to the parent disk, with its differencing disk remaining unaltered, accurately reflects the function of a differencing disk. In fact, when changes are made to a virtual machine that utilizes a differencing disk, those changes are stored only in the differencing disk, keeping the original parent disk intact. This mechanism enables the differencing disk to capture modifications while preserving the baseline state of the parent disk.

The other statements correctly illustrate the properties and uses of differencing disks. For instance, a differencing disk can indeed store various states of the parent disk, which allows for effective snapshots and restorations. It also permits reverting to a previous state of the virtual machine by rolling back to the parent disk if necessary, and it depends on the parent disk for its storage, as the differencing disk does not function independently. These points emphasize the role of differencing disks in virtual machine management, particularly in environments requiring version control and state reversion.