RAID 5 Rebuild and Its Impact on Forensic Recovery
A forensic analyst is examining a RAID 5 array consisting of three disks. One disk has failed and has been replaced. The array is rebuilt automatically. However, the analyst needs to recover deleted files that existed before the rebuild. What is the MOST significant challenge in this scenario?
Quick Answer
The answer is that the rebuild process may overwrite data in slack space and previously unallocated clusters, which is the most significant forensic challenge. This occurs because a RAID 5 rebuild recalculates and writes parity stripes across all disks, including areas that previously held deleted file remnants or slack space. Since the rebuild treats the entire array as a single logical volume, it can overwrite the very unallocated clusters and slack space where a forensic analyst would typically recover deleted files, effectively destroying that evidence. On the CHFI exam, this question tests your understanding of how RAID controller behavior complicates file recovery—a common trap is assuming a rebuild is a simple copy that leaves deleted data intact. Remember: RAID rebuild is a destructive write operation, not a read-only recovery. Memory tip: “Rebuild rewrites; recovery requires pre-rebuild images.”
⚠ Common exam trap
A common mix-up: candidates think the rebuild only affects the failed disk's data, but in reality, the rebuild process writes to all disks in the array, overwriting unallocated space and slack space across the entire volume.
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
✓
The rebuild process may overwrite data in slack space and previously unallocated clusters
When a RAID 5 array with a failed disk is rebuilt, the controller reconstructs data using parity information and writes it to the replacement disk. This rebuild process writes to all previously unallocated clusters and slack space across the array, potentially overwriting the very data the analyst hopes to recover. Deleted files that existed before the rebuild are at high risk of being overwritten during this automatic reconstruction, making recovery extremely difficult or impossible.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
File carving techniques do not work on RAID volumes
Why it's wrong here
Carving can work if data is not overwritten, but rebuild increases overwrite.
- ✓
The rebuild process may overwrite data in slack space and previously unallocated clusters
Why this is correct
Rebuilding RAID 5 writes new parity and data, overwriting free space and slack.
- ✗
The file system becomes corrupted after rebuild
Why it's wrong here
RAID rebuild does not corrupt file system; it restores redundancy.
- ✗
The RAID controller encrypts data, preventing direct disk access
Why it's wrong here
RAID 5 does not inherently encrypt.
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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Same concept, more angles
1 more way this is tested on CHFI
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. An analyst is examining a RAID 5 array of three disks. One disk has failed and been replaced; the array is rebuilding. Which of the following is the most significant forensic challenge regarding data acquisition from this array?
hard- A.The failed disk cannot be imaged because it is physically damaged
- ✓ B.The rebuild process may overwrite unallocated space or remnants of deleted files
- C.RAID 5 arrays cannot be imaged using traditional tools like dd
- D.The array must be imaged while degraded to preserve evidence
Why B: During a RAID 5 rebuild, the array controller reads parity and data from the remaining healthy disks to reconstruct the missing data onto the replacement disk. This process writes to the entire replacement disk, including areas that previously held unallocated space or remnants of deleted files, potentially overwriting critical forensic evidence. The rebuild is a low-level write operation that does not respect file system boundaries, making it a significant challenge for data acquisition.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CHFI practice question is part of Courseiva's free EC-Council 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 CHFI exam.