Lecture 22 - Journaling

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File System Consistency

Data Redundancy

Why Inconsistency is a Problem

Example: Append to /foo/bar

Solution #1: FSCK

Beyond Consistency: Atomicity

Atomicity

Consistency vs. Atomicity

Example: Replace X with Y (where f(X) is redundant)

Journaling

How It Looks

Terminology

Journal Layout

Basic Journaling Walkthrough

Correctness Depends on Ordering

Solution: Barriers

Write Buffering Optimization

Other Optimizations

Reducing the Cost: Metadata-only Journaling

Writeback Journal

Ordered Journaling

Journaling Summary

Source