Nowadays, SSD (fast hard disk) is very popular, but still expensive. Some users want to use some SSD hard disks and some common hard disks to set up a hybrid storage infrastructure, in this case, how does OCFS2 file system utilize these SSD hard disks effectively? so far, we have not any particular optimization, OCFS2 considers these hard disks as one kind of hard disk. So, I want to investigate what we can do in improving OCFS2 under a hybrid storage infrastructure, let OCFS2 be able to aware fast hard disks, and use them more effectively.