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FC0-U71 Practice Question: A server has four hard drives configured in RAID 5
A server has four hard drives configured in RAID 5. One drive fails. What must the technician do to restore full redundancy?
⚠ Common exam trap
Many exam-takers think a simple drive replacement automatically restores redundancy, but they must understand that the array must be explicitly rebuilt (either automatically or manually) to regenerate the missing data from parity.
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
✓
Replace the failed drive and rebuild the array
RAID 5 uses distributed parity across all drives, allowing the array to tolerate a single drive failure without data loss. When a drive fails, the technician must replace the failed drive and then rebuild the array, during which the RAID controller reconstructs the missing data from the parity information on the remaining drives. This restores full redundancy by returning the array to a fault-tolerant state.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Replace all drives and reconfigure RAID
Why it's wrong here
Only the failed drive needs replacement; replacing all is unnecessary.
- ✗
Simply replace the drive with a larger capacity drive
Why it's wrong here
While a larger drive may work, the array must be rebuilt to restore redundancy, not just swapped.
- ✓
Replace the failed drive and rebuild the array
Why this is correct
RAID 5 can rebuild from parity; replacing the failed drive and initiating rebuild restores fault tolerance.
- ✗
Replace the failed drive and restore from backup
Why it's wrong here
Restoring from backup is not necessary since RAID 5 can rebuild from existing parity.
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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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