I was thinking cool,

Amazon thought colder.

Hearsay from Hacker News is that Glacier is not luke-warm short-stoked storage, this is custom low rpm hard drives running custom boards to make extremely low powered extremely cold storage, so low powered racks are only partially provisioned for power:

The reason Glacier is so cheap is because of the custom hardware. They've optimized for low-power, low-speed, which will lead to increased cost savings due to both energy savings and increased drive life. I'm not sure how much detail I can go into, but I will say that they've contracted a major hardware manufacturer to create custom low-RPM (and therefore low-power) hard drives that can programmatically be spun down. These custom HDs are put in custom racks with custom logic boards all designed to be very low-power. The upper limit of how much I/O they can perform is surprisingly low - only so many drives can be spun up to full speed on a given rack.

I hope what Sintaks actually means is, we plugged the maximum possible 108 USB hard drives (4200 rpm green) into a PandaBoard and figured out how to only turn 4 at a time on, then ran the same storage software we run everywhere else. :p

(With seven-port hubs, 18 hubs can support 108 devices, according to http://boards.straightdope.com/sdmb/showpost.php?s=d5437131a58689a0de1b1651ac37d6ce&p=5239848&postcount=5 )
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