Incremental backups only backup changed data (changes archive bit to not backup again if not changed).
Although the incremental backup is fastest to backup, it is usually more time consuming for the restore process.
In some cases, the window available for backup may not be long enough to backup all the data on the system during each backup. In that case, differential or incremental backups may be more appropriate.
In an incremental backup, only the files that changed since the last backup will be backed up.
In a differential backup, only the files that changed since the last full backup will be backed up. In general, differentials require more space than incremental backups while incremental backups are faster to perform. On the other hand, restoring data from incremental backups requires more time than differential backups. To restore from incremental backups, the last full backup and all of the incremental backups performed are combined. In contrast, restoring from a differential backup requires only the last full backup and the latest differential.
The following are incorrect answers:
Differential backups backup all data since the last full backup (does not reset archive bit) Full backups backup all selected data, regardless of archive bit, and resets the archive bit. Disk mirroring is not considered as a backup type.
Reference(s) used for this question: Hernandez CISSP, Steven (2012-12-21). Official (ISC)2 Guide to the CISSP CBK, Third Edition ((ISC)2 Press) (Kindle Locations 20385-20390). Auerbach Publications. Kindle Edition. and HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 2002, chapter 9: Disaster Recovery and Business continuity (page 618).