A Darker Shade of Green: Saving Power in the Datacenter
April 23, 2012
Earth Day, Oxy! While other efforts here at IR have yielded positive results for the environment, there's quite a bit that my team is doing behind the scenes to do our part as well. Earlier, we spoke about our "Centralized Storage" devices. Back then, we were complaining about how it could be difficult to maintain and it begs the question of why bother with such a device at all. The answer, of course, is vastly improved efficiency and in the context of Earth Day, we'll look primarily at power draw. More after the break. Our Oracle 7410 is designed to save power in one key way, by using larger and slower drives compared to smaller, faster ones. We have a total of 92 drives cabled up to our 7410 and each one spins at 7200rpm. Higher-end drives will spin at 10,000rpm or 15,000rpm. As you might imagine, the faster you spin the platters, the more power you need. Our drives are 1TB in size. Back when they were produced, those faster 15,000rpm drives were only readily available in 300GB sizes so we'd need 31/3x as many drives - about 306 - the be able to get the same capacity. According to the manufacturer, our drives draw up to 12.5W each. Those faster drives will draw up to 16.35W each. Adding it all together, our 92 1TB drives spinning at 7,200rpm will only draw 1150W, vs. 5003W for the faster but smaller drives. It doesn't end there, either. Our 92 drives fit into four enclosures. We'd need 13 enclosures for the faster drives and each enclosure sucks up some additional power. There's also the gobs of extra heat those faster drives will generate, which requires more air conditioning to get rid of. Even discounting that (which is handy because I don't know the first thing of calculating power draw with regards to air conditioning), we're still talking about a storage solution that affords us the opportunity to use 67% fewer drives and 77% less power to deliver the equivalent capacity to more expensive options. The net effect is we save 33,752kwh of electricity per year which, according to the EPA's math, is equivalent to planting 597 trees. Granted, those trees will get logged and turned into the paper that you're all still using but we take what we can get.
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