Ext4 now supports volumes of up to 1 exabyte & file of 16 terabyte size. (1 EB = 1 billion gigabytes ). Ext4 has backward compatibility with ext3 which makes it possiible to mount ext3 as ext4. Ext3 is also forward compatible with ext4, it means ext4 may be mounted as ext3 partition.

Ext4 is best filesystem for media streaming and databases. because it does not fill filesystem with 0s to reserve space.

In ext3 the number of subdirectories is limited to 32,000. In ext4 the limit is increased to 64,000. Filesystem after a long time becomes fragmented, ext4 can defragment even a single file too. It can defragment filesystem online. Ext4 has capability of Faster file system checking.