The Dirty Carbon Secret Behind Solid State Memory Drives

Solid state drives use far less power than hard disc drives. But a new study unexpectedly reveals that their lifetime carbon footprint is much higher than their hard disc cousins, raising difficult questions for the computer industry. From a report: The benefits of SSDs over HDDs are legion. They are smaller, mechanically simpler, faster to read and write data than their hard disc cousins. They are also more energy efficient. So with many computer manufacturers and datacenter operators looking to reduce their carbon footprints, it's easy to imagine that all this makes the choice of memory easy. But all is not as it seems, say Swamit Tannu at University of Wisconsin in Madison and Prashant Nair at the University of British Columbia in Vancouver. SSDs have a dirty secret. Tannu and Nair have measured the carbon footprint per gigabyte of these devices across their entire lifetimes and, unexpectedly, it turns out that SSDs are significantly dirtier. "Compared to SSDs, the embodied [carbon] cost of HDDs is at least an order of magnitude lower," say the researchers. Tannu and Nair come to their conclusion by adding up the amount of carbon emitted throughout the estimated 10-year lifespans of these devices. This includes the carbon emitted during manufacture, during operation, for transportation and for disposal. The carbon emitted during operation is straightforward to calculate. To read and write data, HDDs consume 4.2 Watts versus 1.3W for SSDs. The researchers calculate that a 1 terabyte HDD emits the equivalent of 159 kilograms of carbon dioxide during a 10-year operating lifespan. By comparison, a 1 terabyte SSD emits just 49.2 kg over 10 years. But SSDs are significantly more carbon intensive to manufacture. That's because the chip fabrication facilities for SSDs operate at extreme temperatures and pressures that are energy intensive to maintain. And bigger memories require more chips, which increases the footprint accordingly. All this adds up to a significant carbon footprint for SSD manufacture. Tannu and Nair calculate that manufacturing a 1 terabyte SSD emits the equivalent of 320 kg of carbon dioxide. By comparison, a similar HDD emits just 40 kg. So the lifetime footprint for a 1 terabyte SSD is 369.2 kg of carbon dioxide equivalent versus 199 kg for an HDD. So HDDs are much cleaner. That's a counterintuitive result with important implications. At the very least, it suggests that computer manufacturers and cloud data storage operators should reconsider the way they use SSDs and HDDs. For example, almost 40 per cent of the carbon footprint of a desktop computer comes from its SSD, compared to just 4 per cent from the CPU and 11 per cent from the GPU.

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