Re: JFFS2 Support for Large Flash Designs

Jörn Engel
2007-03-07T11:36:32Z

Disclaimer: I am the LogFS developer. Everything below is my personal
opinion based on possibly outdated information. Apply a grain of salt.

On Tue, 6 March 2007 17:38:04 -0800, Johnson, Charles F wrote:
>
> What is this list's opinion of YAFFS ?

Advantages:
o It exists and is working.
o From what I heard it is faster than JFFS2.
o Has a relatively simple design.

Disadvantages:
o Code is not in mainline Linux kernel. I generally distrust such code;
apart from the support question, it is an indication of other problems.
o Only works on raw NAND flash.
o Has O(n) properties, just like JFFS2. It will hit the same
scalability problem at some time in the future.
o No compression support.

Likely the best solution for your problem at the moment.

>> LogFS.

Advantages:
o Code exists.
o Fast mount time (~60ms).
o Has O(1) mount time and memory overhead, O(log(n)) for most other
things, O(sqrt(n)) for GC.

Disadvantages:
o Still under development. Medium format is constantly changing.
o Still has known bugs, see http://lazybastard.org/logfs/BUGS
o Currently needs to write more data to flash than JFFS2/YAFFS.

>> JFFS3

Advantages:
???

Disadvantages:
o To my knowledge, code does not exist (in public) yet.
o Garbage collection was an open issue, last time I looked.

Jörn

--
Invincibility is in oneself, vulnerability is in the opponent.
-- Sun Tzu