"...available as an option when installing Ubuntu 9.04. The
report describes a crash occurring shortly after the KDE 4 desktop
files had been loaded, resulting in the loss of all of the data
that had been created, including many KDE configuration files.
"In a reply, Ext4 Developer Ted Ts'o explains the background of
the problem. Like other modern file systems, such as XFS, Ext4
implements delayed allocation -- writing new data can take up to 60
seconds. This increases the performance and allows for optimisation
of the data organisation on the hard drive platter."