Ok, I searched from Google for quite a while but still cannot find the right solution for me. I have a WD My Book Studio which acts as a primary storage for my photos. I wanna make a "real-time" or "raid-1-like" backup of my photo folder to another Buffalo USB disk drive connecting to the same Mac. So my requirement to the software is that whenever I copy new photos from my SD card to the photo folder in My Book Studio, the software would help me in the background to automatically create another copy to a specific folder in the Buffalo USB disk drive (just like RAID1). It looks simple but I can't find it.... Any buddy can help? Thanks!