Which of the following backup methods takes the MOST time for restoration of data?

An incremental backup only saves data that has changed since the last backup of any type (full or incremental). To perform a full restoration, one must first restore the last full backup and then apply every subsequent incremental backup in the correct sequence. This multi-step process is more complex and time-consuming than restoring from a full backup (one step) or a differential backup (two steps: last full and last differential). The number of files to process and the dependency on a complete, uncorrupted chain of backups make it the longest restoration method.

B. Offsite backup: This describes the location of a backup, not the method. The time to restore depends on the backup method used (e.g., full, incremental) and the connection speed, not just its location.
C. Full backup: This method is the FASTEST for restoration. It requires only one backup set to be restored, as it contains all the data from a specific point in time.
D. Differential backup: Restoration requires only two sets: the last full backup and the most recent differential backup. This is faster than an incremental restore, which may require many sets.

1. National Institute of Standards and Technology (NIST). (2010). Special Publication 800-34 Rev. 1, Contingency Planning Guide for Federal Information Systems. Section 4.3.2, "Backup Types," p. 33. The guide explains that for incremental restores, "the full backup and all of the incremental backups would need to be restored," implying a longer process than other methods.

2. Patterson, D. A., & Hennessy, J. L. (2011). Computer Organization and Design: The Hardware/Software Interface. (Courseware basis for CS61C at UC Berkeley). Chapter 6 discusses storage and dependability, where backup strategies are detailed, highlighting the trade-offs between backup speed and restore speed for different methods.