What type of backup records only the changes made to data blocks on a virtual machine?

• A. Full backup
• B. Differential backup
• C. Incremental backup
• D. Mirror backup

Answer: (C)

The correct answer is incremental backup. Incremental backups are designed to capture only the changes that have occurred since the last backup, which can be either a full backup or the previous incremental backup. This approach optimizes storage use and reduces the backup time because it only focuses on new or modified data blocks on the virtual machine, rather than backing up all the data again.

In a full backup, the entire set of data is backed up, creating a complete copy regardless of what has changed. Differential backups, on the other hand, save changes made since the last full backup, which can lead to larger backup sizes as time goes on because they accumulate changes. Mirror backups create an exact copy of the data at the moment of the backup but do not maintain a history of changes, which is not the focus of the question regarding only capturing changes.

The incremental backup method is especially efficient for virtual machines, where storage space can be limited, and minimizing backup time is crucial.