ScaleDefrag: Design and Implementation of a Scalable File Defragmentation Tool for Flash-based SSDs

ScaleDefrag is a scalable file defragmentation tool for flash-based SSDs.

This repository contains the implementation of the following paper:

ScaleDefrag: Design and Implementation of a Scalable File Defragmentation Tool for Flash-based SSDs,
Sangjin Lee, Sunggon Kim, and Yongseok Son,
PLOS ONE.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0348520

ScaleDefrag extends our previous conference paper:

An Efficient and Parallel File Defragment Scheme for SSDs,
Guangyu Zhu, Jeongeun Lee, Yongseok Son, In Proceedings of 36th ACM/SIGAPP Symposium on Applied Computing, SAC '22.
https://dl.acm.org/doi/abs/10.1145/3477314.3507225

Overview

ScaleDefrag is implemented based on e4defrag and consists of both user-space and kernel-space components.

The user-space component is implemented in:

e2fsprogs/misc/e4defrag.c

The kernel-space component is mainly implemented by modifying the move_extent.c logic in ext4.

Since ext4 is the default file system in many Linux distributions, we forked the ext4 source code and renamed it pxt4 for ease of use and testing. Users can build the pxt4 kernel module and mount it on the target disk to evaluate ScaleDefrag.

ScaleDefrag supports parallel file defragmentation using an asynchronous I/O approach.