ISC2 CC Business Continuity, DR & Incident Response Practice Question
Exhibit
Refer to the exhibit. --- Backup Configuration (extract): - Full backup: Every Sunday at 01:00 - Differential backup: Monday-Saturday at 01:00 - Retention: 30 days --- A server fails on Wednesday at 10:00. The administrator restores from the most recent full backup and applies the latest differential backup. How much data loss is expected?
Based on the backup schedule, what is the maximum potential data loss?
⚠ Common exam trap
ISC2 often tests the distinction between full, differential, and incremental backups, and the trap here is confusing the last full backup as the recovery point when differential backups actually allow restoration to a much more recent point, causing candidates to overestimate data loss.
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
✓
33 hours (data since Tuesday 01:00)
Maximum potential data loss is determined by the interval between the last successful backup and the point of failure. In a differential backup scheme, each differential contains all changes since the last full backup. If the most recent differential backup fails or is unavailable, the last successful backup becomes the previous differential. Here, the backup schedule includes a full backup on Monday at 01:00 and differential backups every 12 hours starting Tuesday at 01:00 (i.e., Tuesday 01:00, Tuesday 13:00, Wednesday 01:00, etc.). To maximize potential data loss, we assume the most recent differential backup (Tuesday 13:00) is lost, so the last successful backup is the differential from Tuesday 01:00. If a failure occurs just before the next scheduled differential (Wednesday 10:00), the data loss spans from Tuesday 01:00 to Wednesday 10:00, which is 33 hours. This is the maximum possible data loss given the schedule. Answer C correctly identifies this.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
9 hours (since Tuesday 01:00)
Why it's wrong here
9 hours would be if failure at 10:00 on Tuesday, not Wednesday.
- ✗
2 days (data since Monday)
Why it's wrong here
Differential on Tuesday includes Monday's data; loss starts from Tuesday 01:00.
- ✓
33 hours (data since Tuesday 01:00)
Why this is correct
Last successful backup was Tuesday 01:00; failure at Wednesday 10:00 = 33 hours.
- ✗
1 day (data since last full backup)
Why it's wrong here
Full backup was Sunday; differential on Tuesday captures changes up to Tuesday 01:00.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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