Então ainda ng testou o ext4?dizem que não é preciso converter pq é compativel com o ext3 mas mesmo assim tenho receio.
Backward compatibility
The ext4 filesystem is backward compatible with ext3, making it possible to mount an ext3 filesystem as ext4 (using the “ext4dev” filesystem type).
[edit] Forward compatibility
The ext4 filesystem is forward compatible with ext3, that is, it can be mounted as an ext3 partition (using “ext3” as the filesystem type when mounting). However, if the ext4 partition uses extents (one of the major new features of ext4), forward compatibility and therefore the ability to mount the filesystem as ext3 is lost. Extents are not used by default; the “extents” option is explicitly required (e.g. mount /dev/sda1 /mnt/point -t ext4dev -o extents