LFCS Storage Management Practice Question
Which two statements are true about LVM snapshots? (Choose two.)
⚠ Common exam trap
Watch out — candidates often assume snapshots are read-only (like many other snapshot implementations) or that they require full duplication of the source volume, but LVM snapshots are read-write by default and use copy-on-write to minimize space usage.
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
✓
Snapshots use copy-on-write technology.
Option C is correct because LVM snapshots are implemented using copy-on-write (COW): when data on the origin logical volume is modified, the original block is copied to the snapshot's COW space before being overwritten, so the snapshot preserves the point-in-time state. Option D is correct because a snapshot can be mounted and its contents copied back to the origin (or the origin can be reverted from the snapshot with lvconvert --merge), making it a valid mechanism for restoring the original volume. Option A is wrong because a snapshot only needs enough space to hold changed blocks, not a full copy of the origin. Option B is wrong because LVM snapshots are writable by default, though they are typically used read-only. Option E is wrong because LVM snapshots operate at the block-device layer and are filesystem-agnostic, working with ext4, XFS, and others.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Snapshots require the same amount of space as the original volume.
Why it's wrong here
Snapshots use a copy-on-write exception store, consuming space only as origin data changes, not a full duplicate. It tempts because thin snapshots can eventually grow to the origin's size, but that is a worst case, not a requirement.
- ✗
Snapshots are read-only by default.
Why it's wrong here
LVM snapshots are writable by default; a read-only attribute exists only if explicitly set. It tempts because snapshots are commonly used for backups, where read-only access is desirable, but that is a configuration choice rather than default behaviour.
- ✓
Snapshots use copy-on-write technology.
Why this is correct
LVM snapshots employ copy-on-write: when a block on the origin changes, its original contents are copied to the snapshot before the write proceeds. This preserves a point-in-time view while consuming space only for modified blocks.
- ✓
Snapshots can be used to restore the original volume.
Why this is correct
LVM snapshots preserve the original volume's block-level state at creation, so reverting writes from the snapshot back to the origin restores that captured point. This satisfies the stem's requirement that snapshots support recovery of the original volume, using the copy-on-write exception store rather than a full duplicate.
- ✗
Snapshots are only supported on ext4 filesystems.
Why it's wrong here
LVM snapshots operate at the block layer, independent of the filesystem above, so ext4, XFS and others are all supported. It tempts because ext4 is common in LVM tutorials, but filesystem type never gates snapshot capability.
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