The correct answer is that thin volumes can be over-provisioned, allowing more virtual space than physical storage, and that the filesystem must support the discard option to reclaim unused blocks. This is because LVM thin provisioning allocates data blocks on demand from a thin pool; without the discard option—or a tool like fstrim—the device mapper never learns that blocks are freed when files are deleted, preventing the thin pool from reclaiming that physical space. On the LPIC-2 exam, this concept tests your understanding of storage efficiency and the interplay between filesystem and volume manager, often appearing as a trap where candidates forget that over-provisioning alone is useless without discard to recover space. A common memory tip: think of discard as the “garbage collector” for thin pools—without it, deleted files leave phantom blocks that waste physical storage.
LPIC-2 Practice Question: Block Devices, Filesystems and Advanced Storage
This LPIC-2 practice question tests your understanding of block devices, filesystems and advanced storage. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Which TWO statements about LVM thin provisioning are correct?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The filesystem on a thin volume must support the 'discard' option to free unused space.
Option B is correct because thin volumes allocate data blocks on demand from a thin pool. To allow the underlying physical storage to reclaim unused blocks when files are deleted, the filesystem must support the 'discard' option (or use fstrim) so that it can notify the device mapper of freed space. Without discard, the thin pool never learns that blocks are no longer in use, preventing space reclamation.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Thin pools are created using the 'pvcreate' command.
Why it's wrong here
Thin pools are created with lvcreate --type thin-pool.
✓
The filesystem on a thin volume must support the 'discard' option to free unused space.
Why this is correct
fstrim or mount -o discard allows space reclamation.
Related concept
Read the scenario before looking for a memorised answer.
✓
Thin volumes can be over-provisioned, allowing more virtual space than physical storage.
Why this is correct
Over-provisioning is a key feature of thin provisioning.
Related concept
Read the scenario before looking for a memorised answer.
✗
Thin provisioning requires a dm-cache device to function.
Why it's wrong here
dm-cache is a separate feature for caching.
✗
Thin volumes automatically grow when they run out of space.
Why it's wrong here
Auto-extension requires monitoring and manual intervention.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume thin volumes automatically grow or that discard is optional, but the exam tests the precise requirement that the filesystem must support and enable discard to free space back to the thin pool.
Detailed technical explanation
How to think about this question
Under the hood, LVM thin provisioning uses a 'thin pool' LV that holds metadata and data blocks. When a thin volume is written to, the device-mapper thin target allocates chunks from the pool. Over-provisioning is possible because the pool only consumes physical space for actually written blocks. In real-world scenarios, if discard is not enabled, a thin pool can fill up even though the filesystem reports free space, leading to unexpected I/O errors; this is why monitoring thin pool usage and enabling periodic fstrim is critical in production.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the LPIC-2 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
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Block Devices, Filesystems and Advanced Storage — This question tests Block Devices, Filesystems and Advanced Storage — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The filesystem on a thin volume must support the 'discard' option to free unused space. — Option B is correct because thin volumes allocate data blocks on demand from a thin pool. To allow the underlying physical storage to reclaim unused blocks when files are deleted, the filesystem must support the 'discard' option (or use fstrim) so that it can notify the device mapper of freed space. Without discard, the thin pool never learns that blocks are no longer in use, preventing space reclamation.
What should I do if I get this LPIC-2 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which TWO statements about LVM thin provisioning are correct?
hard
A.Thin pools automatically extend when they reach 80% usage.
✓ B.It allows creating logical volumes that can be larger than the available physical storage.
C.A thin pool cannot be extended once created.
D.It is only supported on SSDs.
✓ E.Thin snapshots are space-efficient because they share data blocks.
Why B: Option B is correct because LVM thin provisioning allows creating logical volumes that appear larger than the available physical storage (overcommitment). This is achieved by allocating data blocks on demand from a thin pool, rather than reserving them at creation time. The thin pool itself must have sufficient physical storage to accommodate actual writes, but the logical volume size can exceed the pool's capacity.
Last reviewed: Jun 11, 2026
Question Discussion
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This LPIC-2 practice question is part of Courseiva's free LPI 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 LPIC-2 exam.
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