What type of backup involves copying all data items that have changed since the last backup?

The correct answer is incremental backup because this method specifically focuses on capturing all data items that have changed since the last backup was performed, whether that backup was a full or another incremental backup. In this approach, only the data that has been altered or new data that has been created since the last backup is copied, making it efficient in terms of storage space and backup time compared to a full backup.

Incremental backups allow for quicker recovery of the latest data, as they do not require copying all data each time—only the differences from the previous backup. This results in a series of backups that can be sequentially restored to return the system to a particular point in time.

Understanding the other types of backups can clarify why incremental is the distinguishing choice. A full backup, for example, encompasses a complete copy of all data, which does not target only the changes and requires more storage and time. A differential backup also captures data changes, but it differs by copying all changes since the last full backup rather than the last backup of any type, which would generally take longer to execute as multiple versions accumulate. Mirrored backups create an exact copy of the data at a specific point in time but do not regularly capture ongoing changes or operate in a versioned manner.