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It is important to note that the power consumption measures used were the HDD and SSD idle rates, the benchmark that should make SSDs more efficient, not maximum power consumption during IO bursts. In fact, if you compare a measure of W/GB of storage, HDDs are still more efficient per GB of storage than all but a few consumer SSDs designed for laptops.
In regards to bandwidth, measured in W/GB/s, consumer SSDs are significantly more efficient than enterprise options, however the Seagate Enterprise 15K HDD is actually competitive with most of the enterprise SSDs. Only two of the high performance SSDs have efficiencies that are more than 1 W/GB/s less than the Seagate Enterprise 15K HDD efficiency of 5 W/GB/s.
Given this information, the power efficiency gains of using SSDs instead of HDDs that some suggest are minimal if not non-existent in enterprise environments.
While the idea of integrating NAND flash technology into a storage solution to improve performance is not necessarily a bad idea, the ability to do so on a large scale is built on several faulty assumptions regarding SSDs.
First, the optimistic price trends presented ignore real price trends that have not always been reliably downward and have, at times, gone upward.
Second, the assumption that SSDs are cheaper in terms of bandwidth ($/GB/s) and that users will measure costs in this way may be true of the consumer market, but enterprise SSDs are actually more expensive on a $/GB/s basis. No vendor or third party has put forward costs in terms of bandwidth, such as the $/GB/s measure used in this paper. In addition, the assumption that prices will always decrease ignores key market forces, such as supply availability, competition and lack of demand or need for large storage options that have made SSD pricing far more unpredictable than presupposed.
Third, some make no distinction made between consumer SSDs and enterprise SSDs despite the fact that consumer SSDs and enterprise SSDs exist in entirely different market spaces, resulting in significant differences in interfaces, performances, costs and trends between them.
Fourth, these SSD assumptions ignore research that suggests that either reliability, performance, density or a combination of the three must be sacrificed to continue to reduce prices while developing NAND technology in the near future.
Fifth, the assumption that SSDs will require less power today and into the future because they have no moving parts and can idle ignores the complexity of SSD market needs and increased demands for power and applications on enterprise SSDs to ensure reliability and performance.
In the end, flash technology and SSDs cannot yet replace HDDs as primary storage for enterprise and HPC applications due to continued high prices for capacity, bandwidth, and power as well as issues with reliability that can only be addressed by increasing overall costs.
Last but certainly not least is a graphic from EMC:
At least for the foreseeable future, the cost of flash compared to hard drive storage is not going to change.
Photo courtesy of Shutterstock.