SK0-005 security-disaster-recovery Practice Question
A system administrator configures full backups on Sunday evenings and differential backups on weekdays. On Thursday morning, a disk failure occurs. Which of the following sets of backups is necessary to completely restore the server's data with the fewest number of backup files?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Sunday full and Wednesday differential
A differential backup includes all changes since the last full backup. Therefore, only the most recent differential and the last full backup are needed for a complete restore. Using Sunday's full and Wednesday's differential requires just two files, whereas incremental backups would require the full plus every incremental since. Option A (full plus all four differentials) is unnecessary. Option C references a Thursday backup that hasn't occurred yet. Option D ignores all changes since Sunday.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Sunday full only
Why it's wrong here
This would restore only data as of Sunday evening, losing all changes made on Monday, Tuesday, and Wednesday.
- ✗
Sunday full, Monday differential, Tuesday differential, Wednesday differential
Why it's wrong here
This uses four files, which is more than necessary. A differential backup includes all previous changes, so only the latest is needed.
- ✗
Sunday full and Thursday differential
Why it's wrong here
Thursday's differential does not yet exist because the failure occurs in the morning before that backup runs.
- ✓
Sunday full and Wednesday differential
Why this is correct
Correct. Wednesday's differential contains all changes since Sunday, so only these two files are required for a full restore.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed July 2026 · checked against the official CompTIA exam blueprint
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