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Topic starter 01/08/2025 9:55 pm
🧮 Ext4 (Fourth Extended File System) is the default file system for many modern Linux distributions. Introduced in 2008, it builds on Ext3’s foundation with major improvements in performance, reliability, and scalability.
🚀 Key Features
- Journaling: Logs changes before writing them to disk, reducing corruption risk
- Extents: Replaces traditional block mapping with more efficient storage allocation
- Delayed allocation: Improves performance by postponing block assignment
- Multiblock allocation: Allocates multiple blocks at once for faster writes
- Online resizing: Expand file systems without unmounting
- Backward compatibility: Can mount Ext3 and Ext2 volumes
📐 Technical Specs
| Attribute | Ext4 Details |
|---|---|
| Max volume size | Up to 1 exbibyte (EiB) |
| Max file size | Up to 16–256 TiB (depending on block size) |
| Max filename length | 255 bytes |
| Max number of files | ~4 billion |
| Supported OS | Linux, FreeBSD, macOS (via FUSE), Windows (via drivers) |
🧪 Performance Enhancements
- HTree indexing: Speeds up directory lookups
- Preallocation: Reserves space for growing files
- Fast fsck: Reduces file system check time on large volumes
- Nanosecond timestamps: Improves precision for file tracking
⚠️ Ext4 vs Ext3 vs Ext2
| Feature | Ext2 | Ext3 | Ext4 |
|---|---|---|---|
| Journaling | ❌ No | ✅ Yes | ✅ Yes |
| Extents | ❌ No | ❌ No | ✅ Yes |
| Max file size | 2 TiB | 2 TiB | 16–256 TiB |
| Performance | Basic | Moderate | High |
| Reliability | Low | High | Very High |
