This LFCS practice question tests your understanding of storage management. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. 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 system administrator needs to set up software RAID1 on a server for /data. The available disks are /dev/sdb (500GB) and /dev/sdc (1TB). What is the maximum usable capacity of the RAID1 array?
500GB
Correct: RAID1 uses only the smallest disk's capacity for data.
250GB
Why wrong: Incorrect; RAID1 does not halve capacity.
1TB
Why wrong: RAID1 capacity is the size of the smallest disk.
1.5TB
Why wrong: RAID1 mirrors, does not combine capacity.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
500GB
RAID1 (mirroring) writes identical data to all disks in the array, so the usable capacity is limited by the smallest disk. With /dev/sdb at 500GB and /dev/sdc at 1TB, the maximum usable capacity is 500GB. The remaining space on /dev/sdc (500GB) is unusable in the RAID1 array because it cannot be mirrored.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
500GB
Why this is correct
Correct: RAID1 uses only the smallest disk's capacity for data.
Related concept
Read the scenario before looking for a memorised answer.
250GB
Why it's wrong here
Incorrect; RAID1 does not halve capacity.
1TB
Why it's wrong here
RAID1 capacity is the size of the smallest disk.
1.5TB
Why it's wrong here
RAID1 mirrors, does not combine capacity.
Common exam traps
The trap here is that candidates often assume RAID1 adds capacities (like RAID0) or averages them, rather than recognizing that mirroring strictly limits usable space to the smallest disk's capacity.
Detailed technical explanation
Under the hood, Linux mdadm creates a RAID1 array by mapping each logical block to a physical block on each member disk; the array size is set at creation time to the smallest disk's size. If you later add a smaller disk to an existing RAID1, the array must be reshaped or rebuilt. In real-world scenarios, using mismatched disk sizes in RAID1 wastes space on the larger disk, which can be partitioned separately for other uses (e.g., a swap partition or a second array).
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Storage Management — This question tests Storage Management — Read the scenario before looking for a memorised answer..
The correct answer is: 500GB — RAID1 (mirroring) writes identical data to all disks in the array, so the usable capacity is limited by the smallest disk. With /dev/sdb at 500GB and /dev/sdc at 1TB, the maximum usable capacity is 500GB. The remaining space on /dev/sdc (500GB) is unusable in the RAID1 array because it cannot be mirrored.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 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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