Linux has support for a number of file systems and ext3 is one of the most common such. The problem is that ext3 has been around for a while and a real update hasn’t happened for quite some time now, but the developers realized this and started to work on the next version; ext4. This has now appeared as a test version and been included in the latest 2.6.19-RC1 kernel. The new file system support up to 1024 petabyte/volume, which is almost enough for BlueGene/L. The new file system has improved support for prohibting fragmentation, but also the ability to log events and changes to the file system. ext4 will be compatible with ext3 to the extent that you will be able to mount it as ext3, but you will then lose the extra functions.
