CISA Practice Question: Information Systems Operations and Business Resilience
A company uses a RAID 5 array for its file server. One disk fails, and the system continues to operate. However, during the rebuild process, a second disk fails. What is the likely consequence?
⚠ Common exam trap
The trap is assuming RAID 5 can survive any single failure plus a rebuild — candidates forget that the rebuild window is a period of zero redundancy, so a second failure during rebuild is catastrophic.
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
✓
Data loss occurs
RAID 5 tolerates exactly one disk failure by storing distributed parity across all member disks. When one disk fails, the array enters degraded mode and can still serve data by reconstructing missing blocks from parity. However, if a second disk fails before the first is rebuilt, the parity information is insufficient to reconstruct two missing data sets, resulting in complete data loss for the array.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Performance degrades but data remains intact
Why it's wrong here
RAID 5 tolerates only one disk failure; a second failure during rebuild leaves no parity to reconstruct data, so the array fails and data is lost. It is tempting because degraded operation with one failed disk does continue, but that resilience ends once redundancy is exhausted.
- ✗
Data is still available from parity
Why it's wrong here
RAID 5 stores a single parity block per stripe, so it tolerates only one disk failure. With a second disk lost during rebuild, parity cannot reconstruct both missing members, and the volume fails. Parity redundancy suits single-failure tolerance, not concurrent double-disk loss.
- ✗
The system automatically switches to a hot spare
Why it's wrong here
A hot spare only helps if one is configured and still healthy; RAID 5 itself cannot survive two simultaneous disk failures, so the array goes offline and data is lost unless restored from backup. Hot spares suit environments where a spare disk is pre-installed to begin rebuilding automatically after a single failure.
- ✓
Data loss occurs
Why this is correct
RAID 5 tolerates only one simultaneous disk failure, storing parity across all member disks. With one disk already failed, the array runs in degraded mode with no redundancy; a second failure during rebuild leaves insufficient parity to reconstruct missing data, so the volume is lost. This satisfies the stem's double-failure constraint.
Quick reference
RAID Level Comparison
| RAID Level | Min Disks | Fault Tolerance | Read | Write | Usable Capacity |
|---|---|---|---|---|---|
| RAID 0 | 2 | None | Excellent | Excellent | 100% |
| RAID 1 | 2 | 1 disk | Good | Moderate | 50% |
| RAID 5 | 3 | 1 disk | Good | Moderate | 67–94% |
| RAID 6 | 4 | 2 disks | Good | Lower | 50–88% |
| RAID 10 | 4 | 1 disk per mirror | Excellent | Good | 50% |
RAID is not a backup strategy — it protects against disk failure but not against accidental deletion, ransomware, or site-level events.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official ISACA exam blueprint
This CISA practice question is part of Courseiva's free ISACA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CISA exam.