"Because this involved changing the structure of the data stored
on the disk, the programmers decided that rather than introducing
these patches into Ext3, it was time to create a new version of the
file system -- Ext4 -- based on the Ext3 code.
"The result of three years of Ext4 development has been
significant advances from Ext3 which increase the volume limit to
1024 PB. This should be sufficient for many years to come. Extents,
long implemented in other file systems such as XFS, should improve
the efficiency of managing large files. There are also a whole
range of under-the-bonnet changes intended to improve Ext4
performance compared to Ext3."