Btrfs is a new filesystem developed under the aegis of Oracle. ext3/4 while being good for home and small entreprises suffer from lack of advanced features like snapshot i.e. the ablity when you have deleted something to restore filesytem to previous state ,multiple device support i.e. filesytem cannot extent to more than one hardisk/device compression and scalabilty. ext 4 has been called just a stop gap by its developer.
Some of the features its site proclaims are:
* Extent based file storage (2^64 max file size)
* Space efficient packing of small files
* Space efficient indexed directories
* Dynamic inode allocation
* Writable snapshots
* Subvolumes (separate internal filesystem roots)
* Object level mirroring and striping
* Checksums on data and metadata (multiple algorithms available)
* Compression
* Integrated multiple device support, with several raid algorithms
* Online filesystem check
* Very fast offline filesystem check
* Efficient incremental backup and FS mirroring
* Online filesystem defragmentation

This has a 64 bit timestamp on filesystem.
These features will make it one of the most advanced filesystems available.
It is avialable in fedora and fedora 13 having kernel 2.6.33 will have snapshot feature enable.
To use it on fedora type linux icantbelieveitsnotbtr at boot time or you willl not be able to use it.
Currently project has completed 80%.
Btrfs is still experimental. Users are advised to not use it on critical filesystems.

It will use Coherent Remote File System ( CRFS) including NFS currently used.