- A
mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd --metadata=0.90
Why wrong: Metadata 0.90 has a 2TB total limit; each disk 2TB would exceed.
- B
mdadm --create /dev/md0 --level=1 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd
Why wrong: This creates RAID 1 (mirror), not RAID 5.
- C
mdadm --create /dev/md0 --level=0 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd
Why wrong: This creates RAID 0, not RAID 5.
- D
mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd --metadata=1.2
Correct for RAID 5 with metadata 1.2, supporting large disks and auto-assembly.
Question 152 of 513
Create RAID 5 That Reassembles on Boot: Use --metadata=1.2
This LFCS practice question tests your understanding of storage management. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: rAID 5. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A Linux administrator needs to create a RAID 5 array using three disks: /dev/sdb, /dev/sdc, and /dev/sdd, each 2TB. The administrator wants to ensure the array can be reassembled automatically after a reboot. Which command should be used to create the array?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"which command"Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
Quick Answer
The correct command is `mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd --metadata=1.2`, because the `--metadata=1.2` flag stores the superblock at a 4 KiB offset from the start of each disk, which the kernel reads automatically during boot to reassemble the array without manual intervention. This is essential for creating a RAID 5 that reassembles on boot, as older metadata versions (like 0.90 or 1.0) place the superblock at the end of the device, making auto-detection unreliable. On the LFCS exam, this tests your understanding of mdadm metadata versions and how they affect array discovery; a common trap is choosing `--metadata=1.0` or omitting the flag entirely, which would require manual assembly after every reboot. Remember the memory tip: “1.2 is the boot-friendly view” — the “2” in 1.2 reminds you it’s the second offset version that keeps the superblock near the start for automatic reassembly.
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
✓
mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd --metadata=1.2
Option D is correct because it uses `--metadata=1.2`, which stores the superblock at a standard 4 KiB offset from the start of each device, enabling the kernel to automatically discover and assemble the RAID array on reboot without manual intervention. RAID 5 with three disks provides striping with distributed parity, offering a balance of performance and redundancy.
Key principle: RAID 5
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd --metadata=0.90
Why it's wrong here
Metadata 0.90 has a 2TB total limit; each disk 2TB would exceed.
- ✗
mdadm --create /dev/md0 --level=1 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd
Why it's wrong here
This creates RAID 1 (mirror), not RAID 5.
- ✗
mdadm --create /dev/md0 --level=0 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd
Why it's wrong here
This creates RAID 0, not RAID 5.
- ✓
mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd --metadata=1.2
Why this is correct
Correct for RAID 5 with metadata 1.2, supporting large disks and auto-assembly.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
RAID 5
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap is that candidates may choose `--metadata=0.90` (option A) because it is older and familiar, but they overlook the 2 TB per-device size limit. Metadata version 0.90 cannot address disks larger than 2 TB, so it would fail here. Metadata version 1.2 is required for disks over 2 TB and also supports automatic reassembly after reboot.
Detailed technical explanation
How to think about this question
The metadata version determines where the superblock is placed on the disk: version 0.90 places it at the end (last 2 sectors), while version 1.2 places it at a 4 KiB offset from the start, which is within the range the kernel scans during boot (typically the first 64 KiB). In a real-world scenario, using `--metadata=1.2` allows the array to be automatically assembled by the kernel's `md` driver without needing an explicit `mdadm --assemble --scan` or a properly configured `mdadm.conf`, which is critical for systems that may have disks reordered or added after a reboot.
KKey Concepts to Remember
- RAID 5
- mdadm metadata versions
- Automatic array assembly
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
RAID 5
Real-world example
How this comes up in practice
A practitioner preparing for the LFCS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. RAID 5 Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Visual reference
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.
What to study next
Got this wrong? Here's your next step.
Review rAID 5, then practise related LFCS questions on the same topic to reinforce the concept.
- →
Storage Management — study guide chapter
Learn the concepts, then practise the questions
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FAQ
Questions learners often ask
What does this LFCS question test?
Storage Management — This question tests Storage Management — RAID 5.
What is the correct answer to this question?
The correct answer is: mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd --metadata=1.2 — Option D is correct because it uses `--metadata=1.2`, which stores the superblock at a standard 4 KiB offset from the start of each device, enabling the kernel to automatically discover and assemble the RAID array on reboot without manual intervention. RAID 5 with three disks provides striping with distributed parity, offering a balance of performance and redundancy.
What should I do if I get this LFCS question wrong?
Review rAID 5, then practise related LFCS questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
What is the key concept behind this question?
RAID 5
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Last reviewed: Jun 11, 2026
This LFCS practice question is part of Courseiva's free Linux Foundation 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 LFCS exam.
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