I have noticed that Fedora 11 (Leonidas) used ext4fs as file system by default.
Ext4fs main features are:
- Compatibility with ext3FS
- Larger file system support (> 16T)
- larger File Size Support (> 2T)
- Scalability of subdirectories
- Multi Allocation
- Delayed allocation
- fsck faster
- Checksum Journal
- Journal mode
- Online defragmentation
- Persistent pre-allocation
Being Fedora 11 is the base for the development of the new version of RHEL, we can expect a great upcoming Linux distribution.