I’m not entirely sure why anyone would really need an exceptionally slow 4GB RAID array, but this guy did it:
It took something like 11 minutes to copy about 1.8GB from his G5 to the 4GB RAID array, but it’s just proof that it can be done! So if you need to back up data in a flash and all you have on hand is a couple of iPod Shuffles, you too can be like MacGyver and build a quick, easy RAID array. But don’t try and install OS X on it, because while connected Mac OS won’t recognize it as a startup device, and won’t allow you to install the OS to the RAID array.
More details, and the pictures, at the link above.