The best SSDs aren't necessarily the most energy-efficient medium for storage. According to the workloads and drive capacities, a new study from storage provider Scality shows that hard drives can offer between 19% to 94% better power density per drive than SSD.
Unlike SSDs, hard drives have many moving parts, such as mechanical platters or actuator arms. Therefore, the common misperception around SSDs is that they consume less power than hard drives because there aren't any moving mechanisms. That may not be accurate, according to Scality's latest tests. The company's benchmark results reveal that hard drives have a power density advantage over high-density QLC SSDs. Scality used the Micron 6500 ION 30.72TB QLC SSD and the Seagate Exos X22 22TB 7,200 RPM hard drive for comparison. As a quick note, Scality is evaluating power consumption and not performance.
If we look at the TB/watt power-density metric, the hard drive posted 19% read-intensive numbers and 94% write-intensive numbers. At idle, the hard drive consumed 14% more power than the SSD. However, the hard drive had 37% and 68% lower power consumption during active read and write operations. Scality observed similar figures in intensive workloads. For instance, the hard drive consumed 40% and 63% less power in read-intensive and write-intensive workloads, respectively. Scality admitted that the results may change as drive capacities continue to increase in the future.
|Power Data Per Drive||SSD||HDD||HDD Advantage|
|Active read (watts)||15||9.4||37%|
|Active write (watts)||20||6.4||68%|
|Read-intensive workload (avg. watts)||14.5||8.7||40%|
|Write-intensive workload (avg. watts)||18||6.6||63%|
|Power-density read-intensive (TB/watt)||2.1||2.5||19%|
|Power-density write-intensive (TB/watt)||1.7||3.3||94%|
Scality utilized two different models for testing. The read-intensive workload had 10% idle, 80% reading, and 10% writing. On the contrary, the write-intensive workload consisted of 10% idling, 10% reading, and 80% writing. Each drive was in the mentioned power state for the percentage indicated.
Scality noted that "power consumption does not rise to a main criterion on which to base the SSD vs. HDD decision today." It all depends on the workload. For example, SSDs are still the best performance option for read-intensive and latency-sensitive workloads. Meanwhile, hard drives remain the preferred medium for unstructured data workloads.
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This is highly dubious. Which HDD models were compared to which SSD?Reply
What do they mean by power density? energy per Mb, or "power" by Mb. If you consume the same energy in less time, you had higher power, but the same energy.
This article is incredibly disappointing. Scality didn't bother to test or benchmark anything. They say so right in their article.Reply
For each workload profile, drives are assumed to be in the specified power state for the percentage of time indicated.
They took power draw numbers for idle/read/write from the manufacturers and multiplied them by the time percentages. That's it. They didn't make any power measurements. Only 2 drives were compared. And worst of all, they normalized against time, not workload.
They imagined a theoretical scenario in which both drives spent the same amount of time reading/writing/idling. In the real world, drives go back to idling once they finish an operation. The faster drive will spend far more time at idle. And that isn't going to be the mechanical drive.
So it's 5 day old "news" at this point, already been copypasted on another website, and is so dubious that it shouldn't even be posted at all, so why is it being posted about on TH?Reply
Who cares? HDDs are SLOW and noisy. Unless I purposefully keep them spinning, they spin down and make a chatter when they are woken up. I have had several HDDs fail and only one early SSD. I get that they are trying to keep their business alive, but the only reason for HDDs is for large low access storage for less cost, and that is shrinking every year.Reply
Johnpombrio said:Who cares? HDDs are SLOW and noisy. Unless I purposefully keep them spinning, they spin down and make a chatter when they are woken up. I have had several HDDs fail and only one early SSD. I get that they are trying to keep their business alive, but the only reason for HDDs is for large low access storage for less cost, and that is shrinking every year.
If you run a cluster with i dont know, 128, 256, 512 HDD's large, 5W per disk is a big difference. Not everything is based around speed or required absolute speed.
Clearly I'm not the only one who noticed the gaping holes in this comparison. Whether or not the data was gathered from specs rather than experimental observation as another commenter stated, it's a flawed comparison in the first place. Why measure the power consumption of drives meant for different use cases under the same useless condition? If an SSD draws twice the energy but it does so in a quarter of the time, it's used half of the energy that the HDD would to do the same thing.Reply
But the speed also affects the power draw. It's why utility companies measure in Kilowatt Hours, KwH. If your 5W per disk are being drawn for 20s instead of 1m, that's still an overall savings.Vanderlindemedia said:If you run a cluster with i dont know, 128, 256, 512 HDD's large, 5W per disk is a big difference. Not everything is based around speed or required absolute speed.
It's right in the article:vehekos said:This is highly dubious. Which HDD models were compared to which SSD?
"Scality used the Micron 6500 ION 30.72TB QLC SSD and the Seagate Exos X22 22TB 7,200 RPM hard drive"
These datacenter SSDs aren't like the ones in your PC. They have disproportionately higher idle power, which really swings the comparison with HDDs.
This. In datacenters, people talk about density all the time. So, I'm sure they mean power normalized by capacity.vehekos said:What do they mean by power density? energy per Mb,
The source is the most suspicious part. Scality.com describes them as an "Object storage & Cloud Solutions Leader". I think that "publication" which put out the study is basically a PR arm that they use to drive positive press coverage for themselves and their key customers.
Probably because HDD companies are starting to get a bit concerned about QLC SSDs encroaching into more HDD use cases and market niches.Carson365 said:Why measure the power consumption of drives meant for different use cases under the same useless condition?
On the horizon, we can foresee a point where SSDs can be competitive purely on the basis of GB/$, even in cases where their performance isn't required. In such a situation, normalizing by performance would be misguided.
True. They should've adjusted the duty cycle estimates to account for the performance differences.Carson365 said:If an SSD draws twice the energy but it does so in a quarter of the time, it's used half of the energy that the HDD would to do the same thing.
Simply calculating how many watts it takes to transfer 500 gigabytes of data would settle the issue.Reply