LFCS Storage Management Practice Question
A storage administrator wants to create a software RAID 10 (1+0) array using six disks. Which mdadm command is appropriate?
⚠ Common exam trap
Watch out — candidates often confuse the required number of disks for RAID 10 (thinking any even number works, but the command must match --raid-devices to the actual device count) or mistakenly use RAID 1 (--level=1) when the question explicitly asks for RAID 10, leading them to pick option C.
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=10 --raid-devices=6 /dev/sd[abcdef]
It uses the proper mdadm syntax to create a RAID 10 array with six disks. The --level=10 specifies RAID 10 (a striped mirror set), and --raid-devices=6 matches the number of disks provided via the /dev/sd[abcdef] glob, which expands to /dev/sda through /dev/sdf. This command correctly creates a RAID 10 array that combines striping and mirroring across all six devices.
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=10 --raid-devices=6 /dev/sda /dev/sdb /dev/sdc
Why it's wrong here
The command names six RAID devices but supplies only three disks, so mdadm fails to assemble the array. Listing fewer member disks than --raid-devices is valid only when the remaining devices are added later, for example when building a degraded array.
- ✓
mdadm --create /dev/md0 --level=10 --raid-devices=6 /dev/sd[abcdef]
Why this is correct
`--level=10` builds a striped mirror set, and `--raid-devices=6` declares all six member disks, satisfying the stem's RAID 1+0 over six disks constraint. The brace expansion `/dev/sd[abcdef]` supplies exactly six devices, so mdadm creates `/dev/md0` without prompting for missing members.
- ✗
mdadm --create /dev/md0 --level=1 --raid-devices=6 --chunk=64 /dev/sd[abcdef]
Why it's wrong here
--level=1 creates a RAID 1 mirror, not RAID 10; --chunk is ignored for mirrors, and six devices would simply form a six-way mirror. RAID 1 is the right choice when the requirement is maximum redundancy with no striping performance gain.
- ✗
mdadm --create /dev/md0 --level=10 --raid-devices=4 /dev/sda /dev/sdb /dev/sdc /dev/sdd
Why it's wrong here
This command declares four devices while listing only four disks, so it builds a four-disk RAID 10 array, not the six-disk array requested. Specifying --raid-devices=4 is correct when the administrator genuinely wants a smaller array from the available disks.
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.