Tech blog  January 22, 2016

Are SSDs more Power Efficient than HDDs?

Hard disk drives (HDDs) or Solid State Drives (SSDs)? We believe that you should go with SSDs in most cases. In this blog post, however, I’d like to disc uss a factor that we often overlook: power consumption per GB.

Let’s check out a consumer-grade 1TB drive. According to (1/21/2016), WD and Seagates’ 1TB SATA HDD is roughly $50. On the other hand, Samsung’s 1TB SATA SSD is about $290. The price differen ce between these two same-capacity drives is 5.8 times. Considering only these numbers, the HDD seems like a very reasonable choice. (To be honest, I too am surprised that the price of traditiona HDDs have dropped so dramatically.) When using these prices as a point of reference, SSDs should have a 5.8 x value when compared to an HDD.

Most SSD vendors insist, “ SSD’s power consumption is lower than HDD.” That’s true. Especially if you are a CTO or IT manager in an enterprise, you should have a long-term vision. If you plan to use yo ur storage device for 3 years 24/7, the electric bill will definitely affect the total cost of ownership (TCO). Typically, the power consumption for one HDD drive is around 8W, while an SSD will be less t an 5W. However, this is not an apple-to-apple comparison. HDDs generally have higher capacities than their SSD counterparts.

For example, let’s say you are creating an ~8TB storage array. If you choose to go with an HDD, you would only need one drive (for example, the Seagate Archive 8TB). If you chose a flash array, the typica l SSD still only hovers at around a few TBs. In these cases, to match up with that one HDD, you would need to use several SSDs, resulting in the total power consumption of the array to be larger than that one 8TB HDD.

Here we will argue that Watt/GB is a more important factor to consider. The below figure summarizes Watt/GB for each commercially available, high capacity storage device. For this calculation, we used val es on the specifications published by each drive vendor.

According to this result, HDDs are a reasonable option from a power consumption per GB perspective-- if you can accept low I/O performance. However, if high I/O performance is necessary for your applicati n, SSDs are the only choice. In this case, the higher the capacity the SSD is, the better in terms of power consumption it will be.

Do you want to know the power consumption of the 13TB -- the world’s largest SSD? It is currently under measurement, so I cannot disclose that value just yet. However, in our design, the higher the capaci ty of a SSD, the more power efficient it is. So, we know what you are thinking now. Right, just go with the 13TB!

Article by: Akihiro Asahara

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