JFFS2

JFFS2 is the Journaling Flash File System version 2, jffs2 is a log-structured file system for flash memory devices and has support for NAND devices, also Hard links and compression algorithms like zlib, rubin, and rtime.

Jffs2 also has a garbage collection algorithm that eliminates unnecessary I/O.

This article is a stub. You can help the OLPC project by expanding it.

Size of Files

Files in JFFS2 are compressed transparently. This removes some of the need for gzipping and otherwise compressing files to save space. For text files compression rates of 50% or more are possible. du will not show the compressed sizes of files (nor will ls -l).

More discussion is available in this email post.

Algorithms

Zlib

Lossless data-compression library,

• Manual
• Examples

rubin

This simple algorithm is faster than zlib but not quite as effective.

rtime

This is a simple algorithm that often manages to squeeze extra few bytes from data already compressed with gzip

Links

• JFFS2 at Wikipedia
• JFFS at Wikipedia
• Summary on JFFS
• Homepage of JFFS at AXIS
• Logfs