"Announced on Christmas Eve, the EXT4 filesystem is now
declared stable and it is distributed with version 2.6.28 of the
Linux kernel and later. However, the good news is that the EXT4
filesystem was implemented in the upcoming Ubuntu 9.04 Alpha 3 a
couple of days ago and it will be available in the Ubuntu
Installer, if you choose manual partitioning (see the screenshot
below for details). The bad news is that EXT4 will not be the
default filesystem for the Ubuntu OS until version 9.10, due for
release in late October this year.
"OK, OK... so how will the end user benefit from this EXT4
filesystem? Well, first of all, the whole system will be much
faster and more reliable compared to one with EXT3 (I guess that
some of you still remember the Firefox/Ext3 issue), it will boot
faster (the current article proves that) and it's able to handle
files with sizes of up to 16 TB (terabytes). But these are just a
few of the futures brought by the fourth extended filesystem, for
more details you can check the Wikipedia entry for EXT4."