Term: clone

A clone is a form of disk copy that includes data, structure, and the contents of unused areas.

Disks contain both user data and overhead information, as well as structural information, such as partition layout and boot information. Areas of the disk not in use are considered “free” and available, though the disk areas they represent typically continue to hold whatever data had been previously written.

A clone is a bit-for-bit copy of all data and free space, including the physical structure and layout.

Characteristics of a clone include:

• The actual layout is copied. For example, files on the resulting clone will be exactly as fragmented as on the original.
• The contents of unused areas, or “free space,” are copied. If data was recoverable on the original, it would be on the cloned copy also.
• A clone’s size is proportional to the original drive's size, regardless of how much data it contains.

Cloning is often used in mass production of new systems, as well as in some backup strategies.

See What’s the Difference Between a Clone and an Image? for more details, including a comparison to the related term "image."