The current upstream wiki for the EXT4 effort is at http://ext4.wiki.kernel.org/index.php/Main_Page. This page is only retained as a historical reference

EXT3 Filesystem Extents/64bit Project

Recently, many disk vendors are manufacturing disk drives using the perpendicular recording technology, which allows the density of a disk platter to go up to 30 gigabits per square inch, and that translates to 1 terabyte on a 3.5-inch hard drive.

The increase in the disk drive's capacity highlights the need for larger filesystem support. The current limits for ext2/ext3 filesystem are 2 terabytes with 1KB blocks, and 8 terabytes with 4KB blocks. In order to accommodate the growth of disk size in the next 2-5 years, the ext3 filesystem capacity needs to expand, hence the extents/64bit project.

Current Status

Ext4 filesystem has merged into 2.6.19 as a development version. The current features and future plans are documented in http://kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/filesystems/ext4.txt

Ext3 Filesystem Extents

The ext3 extents (a.k.a. 64bit) patchset that has been proposed and submitted upstream for comments. The patchset was originally developed by the developers at Bull; however, there are many other aspects of the ext3 64bit support that weren't addressed by the original patchset. This wiki page is to explain and track the progress of this project:

Bull's opensource website is located at: http://www.bullopensource.org/ext4/

Bull's opensource webpage explains a lot of the changes in the original patchset. Most notably, the EXT3 extents with 64bit physical block patch and 64bit logical block patch.