EMC do some cool stuff with flash/fibre channel/sata storage arrays with software that automatically moves data between the layers as needed, I'm sure I _need_ one of these for my media server: 
<a href="http://www.emc.com/products/detail/hardware/symmetrix-v-max.htm" rel="nofollow">http://www.emc.com/products/detail/hardware/symmetrix-v-max....</a><p>(in that "I _need_ a pony" kind of way...)