Fast Random Number Generation For Encrypted FS?

Signal 11 asks: "I've been reviewing different filesystem-level encryption schemes and so far, I have found only one solution - applying a kernel patch and using the loopback device. The problem is in generating large amounts of random data to seed the initial filesystem - it takes about 16 hours to create 20GB of pseudo-random data from /dev/urandom. Is there a faster (and equally secure) way to generate large amounts of random data?" Any clues? I'd figure a kernel patch to turbocharge /dev/urandom (while not losing too much security) might be another route to take.