CompTIA Security+ (SY0-701)Security ArchitectureMedium
An administrator performs a full backup every Sunday night and a differential backup every other night of the week. The server fails on Thursday morning before that night's backup runs. How many backup sets must be restored to recover the most recent data?
- A2
- B7
- C4
- D1
Show answer & explanationAnswer & explanation
Correct answer: A. 2
Differential backups capture all changes since the last full backup, so only the full backup (Sunday) plus the most recent differential (Wednesday night) are needed to restore data—a total of 2 backup sets, regardless of how many days have passed since the full backup.
Why the other options are wrong
- B. Restoring every daily backup is unnecessary and describes incremental behavior, not differential.
- C. This overcounts; differentials don't need to be chained like incrementals.
- D. A single backup alone would miss either the base data or the accumulated changes.
Differential Backup Restore
A backup strategy where each differential backup contains all changes since the last full backup, so restoration requires only the full backup plus the latest differential.
- Differential size grows each day until next full backup
- Restore = full backup + most recent differential (2 sets)
- Contrasts with incremental, which requires full + every incremental since
Memory trick: Differential remembers everything since Sunday.