Lecture 21 - Log-Structured File System (LFS)

Content locked

The catalog is public. Reading this content requires approved access.

Recap: FFS Placement

Placement Strategy

FFS Policy Summary

Other FFS Features

LFS: Make Writes Sequential

Motivation

Strategy

Big Picture

Data Structures (Attempt 1)

Why That’s Bad

Data Structures (Attempt 2): The Imap

Where to Keep the Imap?

Example Write

Create /foo/bar in LFS

Performance vs FFS

Garbage Collection

LFS GC

GC Operation

GC Mechanism: Block Liveness

Segment Summary (SS)

GC Policy

Problem: Write Amplification

Crash Recovery

Recovery (Roll Forward)

What if a Crash Happens During Checkpoint?

LFS Summary

What Happened to Log Structuring?

Source