I'm running a 2.5" 320GB Toshiba HDD in a bus-powered caddy as disk 1 on my unslung NSLU2. I was tempted to buy a 1TB WD MyBook external HDD which is fanless and has an external power supply. Surprisingly, I find the 2.5" bus-powered drive to be quite noisy. Can anyone comment about which drive they would recommend? Would the 2.5" drive be more susceptible to failure than a 3.5" one if they are both running constantly? Thanks a lot.