6.2. Storage Troubleshooting
Storage problems are uniquely dangerous because they can corrupt data — a filesystem check on a mounted filesystem or a dd command with source and destination reversed can cause catastrophic data loss. Methodical, careful diagnosis is essential.
💡 First Principle: Storage problems fall into four categories: physical (failing hardware → SMART errors, I/O errors in dmesg), logical (filesystem corruption → fsck errors), capacity (disk full → df -h, df -i), and configuration (wrong fstab → mount failures). Identifying the category first determines the correct tool and approach.
⚠️ Common Misconception: "Disk full" errors don't always mean the disk is actually full. Two separate capacity limits can cause this error: block space (checked with df -h) and inodes (checked with df -i). A disk can be 20% full by block space but 100% full on inodes if millions of tiny files were created.
