Are there any well accepted theories as to how these (Nearline & Glacier) systems function? I know with Glacier, I've heard powering down hard-drives, advanced compression (explains 3hr retrieval), and blu-ray storage (explains 3 month minimum). With Nearline bringing access down to 3secs for the same cost, and now with On-Demand IO, I really don't know what to speculate. Assuming I/O is limited due to spread across media, how could that be scaled up on-demand?