hardMultiple Choice
FC0-U71 Practice Question: A company has a server that hosts a critical…
A company has a server that hosts a critical database. The server uses RAID 5 with three disks. One disk fails. What is the immediate impact on data availability?
⚠ Common exam trap
Watch out — candidates often confuse RAID 5 with RAID 0, assuming any disk failure causes total data loss, or they mistakenly think the array becomes completely unavailable until the disk is replaced.
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 is still available, but performance may degrade
RAID 5 uses block-level striping with distributed parity. With three disks, the array can tolerate a single disk failure without data loss because the parity information on the remaining two disks can reconstruct the missing data on the fly. Therefore, data remains fully available immediately after one disk fails, though read and write performance may degrade due to the overhead of parity calculation and reconstruction.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Data is available only after replacing the disk
Why it's wrong here
RAID 5 keeps data accessible immediately in degraded mode, reconstructing missing blocks from distributed parity across the surviving disks. Availability does not wait for a replacement disk; rebuild begins only once one is fitted. This option describes a mirror-less setup requiring manual restoration, not parity-based RAID.
- ✗
The server will shut down
Why it's wrong here
RAID 5 tolerates one disk failure without halting the server; the array continues serving data in degraded mode using parity. A shutdown would occur only if a second disk failed, destroying redundancy. The tempting assumption is that any disk loss is fatal, but that describes RAID 0, which has no parity.
- ✗
All data on the array is lost
Why it's wrong here
With one failed disk in a three-disk RAID 5 array, parity on the remaining disks reconstructs all data, so nothing is lost. Total loss requires a second failure before rebuild completes. The tempting confusion is treating any degraded state as data destruction, which applies to RAID 0 striping without parity.
- ✓
Data is still available, but performance may degrade
Why this is correct
RAID 5 distributes parity across all three disks, so a single disk failure leaves data reconstructable from the surviving disks and parity. The array continues serving data, but reads require parity calculations, degrading performance until the failed disk is rebuilt.
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 by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This FC0-U71 practice question is part of Courseiva's free CompTIA 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 FC0-U71 exam.