hardMultiple Choice
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
Replacing every drive destroys the surviving data and parity, forcing a full rebuild from backup and unnecessary downtime. It appeals as a clean-slate fix, yet RAID 5 tolerates one failed member, so only that disk needs swapping and reconstruction.
- ✗
Simply replace the drive with a larger capacity drive
Why it's wrong here
A larger drive alone does not rebuild the missing parity data; the array stays degraded until the replacement is added and the controller reconstructs parity across all four members. Capacity matching matters because the controller treats the smallest member as the array size, wasting the extra space.
- ✓
Replace the failed drive and rebuild the array
Why this is correct
RAID 5 stores parity across all member disks, letting data be reconstructed from the surviving three drives. Fitting a replacement disk and rebuilding restores redundancy; until the rebuild completes, the array runs degraded with no further fault tolerance.
- ✗
Replace the failed drive and restore from backup
Why it's wrong here
Restoring from backup recovers file data but does not rebuild the RAID 5 parity stripe; redundancy returns only when the controller reconstructs parity onto the replacement drive. Backups suit data loss or corruption, not a single-disk failure where parity already protects the data.
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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