Which backup method is additive because the time and tape space required for each night’s backup grows
during the week as it copies the day’s changed files and the previous days’ changed files up to the last full
backup?

A.
The differential backup method.

B.
The full backup method.

C.
The incremental backup method.

D.
The tape backup method.

Explanation:
The Differential Backup Method is additive because the time and tape space required for each night’s backup
grows during the week as it copies the day’s changed files and the previous days’ changed files up to the last
full backup.
Archive bits let the backup software know what needs to be backed up. The differential and incremental backup
types rely on the archive bit to direct them.
Incorrect Answers:
B: Full backups back up all files. Full backups are not additive.
C: Incremental backups are not additive because they reset the archive bit so the file is not backed up again
next day (unless the file was changed again).
D: The tape backup method is not a method that determines whether the archive bit is reset or not; it just
specifies that the files are backed up to tape.

Krutz, Ronald L. and Russel Dean Vines, The CISSP Prep Guide: Mastering the Ten Domains of Computer
Security, John Wiley & Sons, New York, 2001, p. 69
http://www.brighthub.com/computing/windows-platform/articles/24531.aspx