LFCS Storage Management Practice Question
A system administrator wants to create a RAID 1 array using two whole disks /dev/sdb and /dev/sdc. They plan to use mdadm. Which command creates the array and builds it with two devices?
⚠ Common exam trap
Test-takers frequently confuse `--raid-devices` with `--raid-disks` or misuse `--add` for creation, leading them to pick options that either use invalid syntax or perform the wrong operation entirely.
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=1 --raid-devices=2 /dev/sdb /dev/sdc
It uses the proper mdadm syntax to create a RAID 1 array: `--create` to initialize the array, `--level=1` (or `--level=raid1`) to specify mirroring, `--raid-devices=2` to indicate exactly two disks, and lists both `/dev/sdb` and `/dev/sdc`. This command builds the array with the two specified whole disks, which is the standard method for creating a RAID 1 array in Linux.
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=mirror --raid-disks=2 /dev/sdb /dev/sdc
Why it's wrong here
--raid-disks is incorrect; should be --raid-devices. Also 'mirror' is an alias for 1 but may not be consistent.
- ✗
mdadm --create /dev/md0 --level=raid1 --add /dev/sdb /dev/sdc
Why it's wrong here
--add is not used for creation; it's for adding a device to an existing array.
- ✓
mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sdc
Why this is correct
Correct syntax for creating RAID1.
- ✗
mdadm --assemble /dev/md0 /dev/sdb /dev/sdc
Why it's wrong here
--assemble is for assembling an existing array, not creating.
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 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.