no support for the mmap or sendfile system calls, they also use a different on-disk format from regular files. There is also an "inherit-journal" attribute which when set on a directory causes all files (and sub-directories) created within that directory to have the journal (or inherit-journal, respectively) flag set. This can be used instead of the data=journal mount option which ext3 supports (and GFS/GFS2 does not).
