LFCS Storage Management Practice Question
An administrator is preparing a new server that will use software RAID 1 for the root filesystem. The system has two identical 500 GB disks, /dev/sda and /dev/sdb. The administrator wants to create the RAID array and then place LVM on top of it. Which command correctly creates the RAID 1 array using the entire disks?
⚠ Common exam trap
The trap here is mixing up mdadm --create with mdadm --assemble, or specifying the wrong RAID level for the required redundancy.
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/sda /dev/sdb
Creating a RAID 1 array on whole disks requires mdadm --create with --level=1 and --raid-devices=2, followed by the device paths. RAID 1 provides mirroring for redundancy. Using --level=0 would create a stripe with no redundancy, and --assemble is only for activating existing arrays. The correct device paths are the whole disks, not partitions.
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=0 --raid-devices=2 /dev/sda /dev/sdb
Why it's wrong here
This creates a RAID 0 (stripe) array, not RAID 1. RAID 0 provides no redundancy, so a single disk failure would destroy the array. The scenario requires RAID 1 for mirroring, making this option incorrect despite using the correct mdadm syntax for a different RAID level.
- ✗
mdadm --assemble /dev/md0 /dev/sda /dev/sdb
Why it's wrong here
mdadm --assemble is used to activate an existing RAID array from its component devices, not to create a new one. Since no RAID metadata exists on these disks yet, assembly would fail. The --create option is required to initialize a new array with the desired RAID level and device count.
- ✗
mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1
Why it's wrong here
This command attempts to create RAID 1 using partitions /dev/sda1 and /dev/sdb1, but the scenario specifies using the entire disks. Unless those partitions already exist and are sized appropriately, the command will fail. The administrator intends to use whole disks, so the correct device paths are /dev/sda and /dev/sdb.
- ✓
mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda /dev/sdb
Why this is correct
mdadm --create with --level=1 and --raid-devices=2 creates a RAID 1 array named /dev/md0 using the two specified disks. This is the correct syntax to initialize a mirrored array on whole disks. After creation, the administrator can create LVM physical volumes on /dev/md0 and proceed with volume group and logical volume setup.
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 and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Linux Foundation exam blueprint
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.