Question 66 of 144
SK0-005 troubleshooting Practice Question
A server running a critical database application crashes and fails to boot with the error message 'Operating System not found.' The server is equipped with a hardware RAID 5 array consisting of three identical disks. A technician suspects a disk failure. What is the MOST likely cause of this error?
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
✓
Two or more disks have failed.
Option D is correct because RAID 5 can tolerate a single disk failure and continue operating in a degraded state. The 'Operating System not found' message indicates the RAID array is offline or the boot volume is inaccessible, which most commonly happens when two or more disks fail simultaneously, exceeding the redundancy of RAID 5. Option A would not cause this error; a single failure would allow the OS to boot. Option C is less common and might produce different errors. Option B could happen but is normally a second-order effect.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
A single disk has experienced a complete failure.
Why it's wrong here
A healthy RAID 5 array continues to function with one failed disk; the OS would still boot.
- ✗
The boot sector on the disk is corrupted.
Why it's wrong here
Boot sector corruption is possible but less likely given the context of a sudden crash and a RAID array; the controller typically manages the boot process.
- ✗
The RAID controller firmware is corrupted.
Why it's wrong here
Corrupted firmware might cause boot issues, but it is uncommon and often manifests with different POST errors.
- ✓
Two or more disks have failed.
Why this is correct
RAID 5 cannot survive a second disk failure; the array goes offline, making the OS inaccessible.
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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Last reviewed: Jul 26, 2026
This SK0-005 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 SK0-005 exam.
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