# journaling file system

> file system that keeps track of not yet committed changes in a data structure called a “journal” (usually a circular log); when a system crash or power failure occurs, such file systems can be recovered online faster with less corruption

**Wikidata**: [Q579047](https://www.wikidata.org/wiki/Q579047)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Journaling_file_system)  
**Source**: https://4ort.xyz/entity/journaling-file-system

## Summary
A journaling file system is a type of file system that maintains a journal (typically a circular log) to track changes before they are committed, allowing faster recovery from crashes or power failures with less data corruption.

## Key Facts
- It's a type of file system that keeps track of not yet committed changes in a data structure called a "journal" (usually a circular log)
- When a system crash or power failure occurs, such file systems can be recovered online faster with less corruption
- It's classified as a subclass of file system
- Related file systems include Btrfs, XFS, and ReiserFS
- It's used with intent log functionality
- Has aliases including "日誌檔案系統", "日誌式", and "نظام الملفات المزود بقيد حوادث"
- Has a sitelink count of 25
- The Wikipedia page is available in multiple languages including Arabic, Bulgarian, Catalan, Czech, German, English, Spanish, Persian, Finnish, French

### Q: What is the main purpose of a journaling file system?
A: It keeps track of not yet committed changes in a data structure called a "journal" to allow faster recovery from crashes or power failures with less data corruption.

### Q: How does journaling file system work?
A: It maintains a journal (usually a circular log) to track changes before they are committed to the main file system.

### Q: What are some examples of journaling file systems?
A: Examples include XFS (created by Silicon Graphics in 1993), Btrfs (developed at Oracle since 2007), and ReiserFS.

## Why It Matters
Journaling file systems address the critical problem of data corruption and recovery time after system failures. Traditional file systems require a full fsck (file system check) after crashes, which can be time-consuming and potentially lead to data loss. Journaling systems maintain a log of changes, allowing the system to recover quickly and with minimal data loss. This has significantly improved reliability and availability of storage systems, particularly in environments where system crashes are common or where data integrity is critical. The ability to recover online without rebooting or extensive manual intervention has become essential for modern computing systems.

## Notable For
- First implemented in XFS in 1993 by Silicon Graphics, Inc.
- Used the copy-on-write principle in Btrfs since 2007
- Maintains a circular log structure for journaling
- Provides faster recovery from crashes compared to traditional file systems
- Supports multiple languages as indicated by its Wikipedia page

## Body
### Technical Implementation
Journaling file systems typically maintain a journal (often implemented as a circular log) that records changes before they are committed to the main file system structure. This approach allows the system to recover from crashes by replaying the journal entries rather than performing a full file system check.

### Recovery Process
When a system crash occurs, the journaling file system can recover online by replaying the journal entries in order. This process is significantly faster than traditional file systems which require a full fsck operation that scans the entire file system structure.

### Performance Characteristics
The circular log structure ensures that the journal can be written continuously without needing to rewind, providing efficient tracking of changes. This design minimizes the risk of journal corruption during system failures.

### Evolution and Variations
Over time, different journaling file systems have been developed with varying implementations. XFS, created by Silicon Graphics in 1993, was one of the first major implementations. Later systems like Btrfs introduced additional features like copy-on-write functionality.

### Language Support
The journaling file system concept has been documented and explained in multiple languages, indicating its widespread adoption and importance across different computing communities.

## References

1. Freebase Data Dumps. 2013
2. [OpenAlex](https://docs.openalex.org/download-snapshot/snapshot-data-format)