LFCS Storage Management Practice Question
An administrator is preparing a new server with two unused disks, /dev/sdb and /dev/sdc, for a software RAID 1 array that will hold customer data. Which two commands are required to create the array and make it usable? (Choose two.)
⚠ Common exam trap
Candidates often confuse mdadm --create with mdadm --assemble, since both produce an active /dev/md device but only one works on blank disks.
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
Creating a usable software RAID 1 array requires two actions: mdadm --create to build the array from the member disks, and a filesystem creation command such as mkfs.ext4 on the resulting /dev/md0 device. Assembly is only for reactivating existing arrays, and pvcreate belongs to LVM. Verification with mdadm --detail is optional.
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=1 --raid-devices=2 /dev/sdb /dev/sdc
Why this is correct
This mdadm command creates a RAID 1 array named /dev/md0 using the two specified disks as members. It is the essential step that assembles the array. After creation, the array appears as a block device that can be partitioned or formatted. Without this command, no RAID device exists, so the remaining steps would have nothing to act on.
- ✗
mdadm --detail /dev/md0
Why it's wrong here
mdadm --detail displays information about an existing array, such as its level, state, and member devices. It is a reporting command, not a creation or formatting step. While useful for verification, it does not make the array usable and is not required to set it up.
- ✗
pvcreate /dev/sdb /dev/sdc
Why it's wrong here
pvcreate initializes disks as LVM physical volumes, which is a different storage technology from software RAID. Running it would overwrite the RAID metadata and prevent mdadm from managing the disks. LVM can be layered on top of RAID, but it is not part of creating the RAID 1 array itself.
- ✗
mdadm --assemble /dev/md0 /dev/sdb /dev/sdc
Why it's wrong here
mdadm --assemble is used to activate an existing array whose metadata is already on the member disks, typically after a reboot or when moving disks between systems. It does not create a new array from blank disks. In this scenario the disks are unused, so there is no existing metadata to assemble.
- ✓
mkfs.ext4 /dev/md0
Why this is correct
Once the RAID array exists as /dev/md0, it must be formatted with a filesystem before it can store data. mkfs.ext4 writes an ext4 filesystem onto the array. This is a required step in making the array usable. The array can also be formatted with other filesystems, but a filesystem is necessary regardless.
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 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.