Emergic: Rajesh Jain's Blog

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Internet’s Energy Needs

October 22nd, 2005 · No Comments

Bob Cringely does some calculations for all the free services on offer:

Let’s imagine some typical numbers. In the U.S. alone, according to Nielsen/Netratings, we have approximately 202 million Internet users, each of whom is eligible for a free Gmail account with two gigabytes of storage. Since my mother uses less than two gigs and I use more, let’s do our rule-of-thumb estimate with that number, making the potential Gmail storage obligation 404 million gigabytes or about 400 petabytes. That’s 400 times the current capacity of the Internet Archive, but it is also probably a tenth or less the total capacity of our PC and DVR hard drives today, so I think it is a very fair number to play with.

Probably 80 percent of this capacity will be borne by the major players, with each of those taking a roughly equal share. That’s MSN, Yahoo and Google, assuming that AOL will be somehow distributed between them, with each having about 100 petabytes of storage.

How much storage IS that, really? Well, the biggest enterprise hard drives available today hold 400 gigabytes each, which means each of these companies is going to need AT LEAST 250,000 drives, making Seagate, Hitachi, Maxtor, and Western Digital all very happy. Though with volume discounts that’s really only about $25 million in disk drives — far less than Microsoft’s legal bills.

Now let’s build a data center using those 250,000 drives. A disk array can hold about 32 drives in a 3U space. In a typical cabinet you can store about 12 arrays or a total of 384 drives. That cabinet sits on a 2′ x 2′ floor tile, plus some aisle space, or about 10 square feet of floor space for planning purposes. 250,000/384=651 cabinets or about 6,500 square feet. Heck, that’s nothing when you read about all the hosting companies, with their 20,000 square foot data centers containing 20,000 servers each.

The problem comes when you start to think about power consumption. It’s not that disk drives consume so much power or that they haven’t come down in consumption over the years, but each of those cabinets will require using modern drives about 3,300 watts to run while the full 100 petabytes will require 2.148 MEGAwatts. And all that heat has to go somewhere, so the building will typically use three to four times as much power for air conditioning as it does to run the drives, taking our total power consumption up to just under 10 megawatts, which at typical U.S. industrial power rates will cost about $5 million per year.

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