"Flash forward to the present and let us take a look at
Ext4-fs and Btrfs. A lot of journalists/bloggers have been doing a
lot of comparisons between the two and unless I am mistaken, both
attempt to resolve two different problems. Ext4-fs (an upgrade to
the Ext3-fs desktop file system) will still be a "desktop file
system" while Btrfs is a solution to compete with the Sun
Microsystems enterprise capable ZFS. Both are to be utilized in
completely different arenas."