- A
Recreate the RAID 5 array from scratch using all three healthy disks (sdb, sdc, sdd) and restore data from backup.
Why wrong: Unnecessarily destructive; rebuilding can preserve data.
- B
Run 'mdadm --manage /dev/md0 --fail /dev/sda --remove /dev/sda', then 'mdadm --manage /dev/md0 --add /dev/sdd'.
The standard procedure: fail and remove the failed disk, then add the spare, triggering a rebuild.
- C
Run 'mdadm --manage /dev/md0 --add /dev/sdd' to directly add the new disk and let the array rebuild automatically.
Why wrong: The failed disk must be removed first; adding without removal may cause conflicts.
- D
Use LVM to mirror the two healthy disks and ignore the failed one, ensuring data redundancy.
Why wrong: LVM does not provide RAID 5 functionality and would require reconfiguration, losing the benefit of RAID 5.
LFCS Storage Management Practice Question
This LFCS practice question tests your understanding of storage management. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 Linux server at a hosting provider uses a software RAID 5 array with three 2 TB disks (sda, sdb, sdc) configured as /dev/md0, hosting a large ext4 filesystem. The server experiences a performance degradation and I/O errors. The administrator checks /proc/mdstat and sees that /dev/sda is marked as failed. The remaining two disks are still active. The administrator has a spare disk /dev/sdd of the same size. The filesystem is sparse and can tolerate downtime. What is the most appropriate course of action to restore the array to a fully functional state with 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
Run 'mdadm --manage /dev/md0 --fail /dev/sda --remove /dev/sda', then 'mdadm --manage /dev/md0 --add /dev/sdd'.
Option B is correct because the proper procedure is to first mark the failed disk as failed in the MD array, remove it, then add the new disk, which triggers a rebuild. Option A is wrong because simply adding the new disk without removing the failed one will not work; the array still has a failed disk. Option C is wrong because recreating the array destroys existing data. Option D is wrong because LVM does not have native RAID capabilities and this would not utilize the existing RAID metadata.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Recreate the RAID 5 array from scratch using all three healthy disks (sdb, sdc, sdd) and restore data from backup.
Why it's wrong here
Unnecessarily destructive; rebuilding can preserve data.
- ✓
Run 'mdadm --manage /dev/md0 --fail /dev/sda --remove /dev/sda', then 'mdadm --manage /dev/md0 --add /dev/sdd'.
Why this is correct
The standard procedure: fail and remove the failed disk, then add the spare, triggering a rebuild.
Related concept
Static NAT maps one inside address to one outside address.
- ✗
Run 'mdadm --manage /dev/md0 --add /dev/sdd' to directly add the new disk and let the array rebuild automatically.
Why it's wrong here
The failed disk must be removed first; adding without removal may cause conflicts.
- ✗
Use LVM to mirror the two healthy disks and ignore the failed one, ensuring data redundancy.
Why it's wrong here
LVM does not provide RAID 5 functionality and would require reconfiguration, losing the benefit of RAID 5.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related LFCS NAT questions on configuration and troubleshooting.
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FAQ
Questions learners often ask
What does this LFCS question test?
Storage Management — This question tests Storage Management — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Run 'mdadm --manage /dev/md0 --fail /dev/sda --remove /dev/sda', then 'mdadm --manage /dev/md0 --add /dev/sdd'. — Option B is correct because the proper procedure is to first mark the failed disk as failed in the MD array, remove it, then add the new disk, which triggers a rebuild. Option A is wrong because simply adding the new disk without removing the failed one will not work; the array still has a failed disk. Option C is wrong because recreating the array destroys existing data. Option D is wrong because LVM does not have native RAID capabilities and this would not utilize the existing RAID metadata.
What should I do if I get this LFCS question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related LFCS NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 24, 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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