Journaling file systems in Operating Systems - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

How journaling improves file system reliability

Which of the following best explains how a journaling file system improves reliability after a sudden power failure?

A It writes all data twice to ensure no data loss occurs.

B It compresses files to reduce the chance of corruption.

C It records changes in a log before applying them to the main file system, allowing recovery after crashes.

D It encrypts file data to prevent unauthorized access during failures.

💡 Hint

Think about how the system keeps track of changes before making them permanent.

Journaling file systems write changes to a special log (journal) first. If a crash happens, the system can replay or discard incomplete changes from the journal, preventing corruption.

📋 Factual

intermediate

Common journaling file systems

Which of the following is a widely used journaling file system in Linux?

A ext4

B NTFS

C FAT32

D HFS+

💡 Hint

It is the default file system for many Linux distributions.

ext4 is a popular journaling file system used in Linux. FAT32 does not support journaling, NTFS is used mainly in Windows, and HFS+ is used in older macOS versions.

🔍 Analysis

advanced

Journaling modes and performance trade-offs

Consider three journaling modes: writeback, ordered, and journal. Which mode offers the best balance between data safety and performance?

A Ordered mode, because it writes metadata to the journal but data directly, ensuring consistency with moderate speed.

B Writeback mode, because it writes data and metadata asynchronously for speed.

C Journal mode, because it writes both data and metadata to the journal for maximum safety.

D None, all modes have the same performance and safety.

💡 Hint

Think about how data and metadata are handled differently in each mode.

Ordered mode journals metadata but writes data directly, preventing metadata corruption while maintaining better performance than full journaling (journal mode). Writeback mode is fastest but less safe.

❓ Comparison

advanced

Difference between journaling and copy-on-write file systems

Which statement correctly contrasts journaling file systems with copy-on-write (COW) file systems?

A Journaling file systems compress data, while COW file systems encrypt data.

B Journaling file systems always use more disk space than COW file systems.

C COW file systems do not protect against data corruption, unlike journaling file systems.

D Journaling file systems write changes to a log before applying them; COW file systems write new copies of data to avoid overwriting existing data.

💡 Hint

Focus on how each system handles data changes.

Journaling logs changes before applying them to maintain consistency. COW creates new copies of data blocks for changes, preserving original data until new writes complete.

❓ Reasoning

expert

Impact of journaling on system crash recovery time

Why does a journaling file system typically reduce the time needed to recover from a system crash compared to a non-journaling file system?

A Because it stores a complete backup of all files on the disk.

B Because it can quickly replay or discard incomplete operations recorded in the journal instead of scanning the entire disk.

C Because it disables write caching to prevent data loss.

D Because it automatically repairs hardware errors during boot.

💡 Hint

Consider what the system needs to do after a crash to restore consistency.

Journaling file systems keep a log of recent changes. After a crash, the system only needs to check this log to fix or discard incomplete changes, avoiding a full disk scan.