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File systems are the invisible architecture that determines how your operating system stores, retrieves, and protects data. When you're tested on this material, you're not just being asked to name file systems—you're being asked to understand why different systems exist and what trade-offs they make. The concepts at play include journaling for crash recovery, metadata management, storage efficiency, and platform-specific optimization.
Think of file systems as the organizational strategy for your hard drive. Some prioritize compatibility across devices, others prioritize data integrity through journaling, and newer systems optimize for flash storage characteristics. Don't just memorize which OS uses which file system—know what problem each one solves and why an administrator might choose one over another.
These file systems prioritize broad compatibility over advanced features. They're the "universal translators" of storage—readable by almost anything, but with significant limitations.
The trade-off: maximum portability comes at the cost of modern features like journaling, large file support, and security.
Compare: FAT vs. ReiserFS—both are largely legacy systems, but for opposite reasons. FAT survives due to universal compatibility despite poor performance; ReiserFS offered excellent small-file performance but lost relevance as other systems caught up. If an FRQ asks about cross-platform storage, FAT is your answer.
Journaling file systems maintain a log (journal) of changes before committing them to disk. If the system crashes mid-write, the journal enables recovery without full disk scans.
The mechanism: write intentions to the journal first, then execute. On crash recovery, replay or discard incomplete transactions.
Compare: ext4 vs. XFS—both are journaling file systems for Linux, but ext4 prioritizes general-purpose reliability while XFS optimizes for parallel I/O and large files. For an exam question about a video editing workstation on Linux, XFS is the better answer.
These file systems are tightly integrated with their parent operating systems, trading cross-platform compatibility for deep OS integration and optimized performance.
The principle: when you control both the OS and the file system, you can optimize for specific hardware and use cases.
Compare: HFS+ vs. APFS—both are Apple-exclusive, but APFS represents a ground-up redesign for flash storage rather than spinning disks. Key exam distinction: APFS supports cloning (instant file copies that share storage until modified) and snapshots natively.
Copy-on-write (COW) file systems never overwrite data in place. Instead, they write new data to a different location and update pointers. This enables powerful features like snapshots and self-healing.
The mechanism: modifications create new blocks rather than overwriting existing ones, preserving previous states automatically.
Compare: ZFS vs. Btrfs—both are copy-on-write systems with snapshots and checksumming, but ZFS is more mature and feature-complete while Btrfs is GPL-licensed and Linux-native. For exam questions about data integrity and self-healing storage, ZFS is the canonical example.
| Concept | Best Examples |
|---|---|
| Universal compatibility | FAT |
| Windows standard with security | NTFS |
| Linux general-purpose | ext4 |
| High-performance parallel I/O | XFS |
| Flash/SSD optimization | APFS |
| Copy-on-write with self-healing | ZFS, Btrfs |
| Integrated volume management | ZFS |
| Apple ecosystem | HFS+, APFS |
| Low CPU overhead | JFS |
| Small file optimization (legacy) | ReiserFS |
Which two file systems use copy-on-write architecture and support automatic data integrity verification through checksumming?
A system administrator needs to format a USB drive that will be used across Windows, macOS, and Linux machines. Which file system should they choose, and what limitation will they face?
Compare ext4 and XFS: both are Linux journaling file systems, but when would you specifically recommend XFS over ext4?
What distinguishes APFS from its predecessor HFS+, and why did Apple make this change?
FRQ-style prompt: Explain how journaling improves crash recovery compared to non-journaling file systems. Identify two file systems that implement journaling and describe one additional feature each provides beyond basic journaling.