SSDs Kill The 15K HDD, Seagate Rolls Out Last Generation

The venerable 15K HDD is singing its swan song as Seagate introduces its sixth-generation Enterprise Performance 15K HDD v6, which will be the last mission-critical 15K HDD the company produces.

Seagate representatives indicated that the company is not working on future generations of 15K HDDs due to the proliferation of SSDs in the data center. The company will offer the Enterprise Performance 15K HDD v6 (otherwise known as the 15K.6) for an extended period of time to ensure that forward compatibility and replacements are on hand, as it does all of its data center HDDs, but it will offer SSDs as the go-to solution for high-performance workloads. The move isn't entirely surprising; it's fair to say that the 2.5" HDD segment has been on a managed decline (albeit a steep one) recently. The "mission-critical" 2.5" segment declined from roughly five million units in 4Q2014 to 3.2 million in 1Q2016.

We know that HGST also has another generation of 15K data center HDDs in the works, unlike its parent WD, which abandoned the segment years ago. Toshiba also has another series in development, but we are unsure if the companies also plan to end their 15K product lines.

Both Toshiba and WD have tremendous flash production capabilities, unlike Seagate, which relies upon a strategic alliance with Micron for its flash. It's a fair bet that WD and Toshiba, with their own captive NAND supply, would be more interested in abandoning the segment than Seagate is, so we expect them to also halt 15K HDD development.

The migration from 15K HDDs to SSDs was somewhat inevitable, as SSDs offer tremendous advantages in performance, power, and density. The performance and power consumption characteristics between SSDs and HDDs aren't really comparable (SSDs win hands down), but 2.5" HDDs enjoyed some measure of stability for the last several years due to their density and price advantage. Both of those advantages are waning in the era of cheap 3D TLC NAND. Some enterprise SSDs reach up to 32TB in the 2.5" form factor, and for comparison, the new Seagate 15K.6 tops out at a mere 900GB.

The HDD vendors do have several tricks up their sleeve to increase density, such as helium and SMR, but neither of those new technologies have wormed their way into the 15K segment. SMR suffers crushing performance penalties during random write workloads, which is the target segment for 15K HDDs, so it makes sense that the vendors do not use it. However, helium surprisingly remains a no-show in the 2.5" segment. The continued vendor focus on high-density products, such as the standard 7,200RPM 3.5" HDDs, indicates that the vendors probably aren't interested in spending the R&D capital to infuse the withering 2.5" segment with helium technology.

15K HDDs tend to be a high-margin product for HDD vendors, largely due to the increased price of SAS models, but SSD pricing continues to plunge as SSD vendors build scale and continue to penetrate the data center. Relatively cheap SAS SSDs with 3D TLC NAND have swept over the data center, and the SSD manufacturers aren't as prone to charge hefty premiums for SAS models. SSDs have always offered long-term price advantages due to their increased performance and density, which come along with lower power consumption--a key metric in the data center. However, these advantages were tough long-term selling points when HDDs had a significant up-front pricing lead, but now that SSD pricing has plunged further, the issue has turned into a no-brainer.

SSDs can now compete on both density and cost, but a straight price comparison of one SSD to one HDD isn't accurate. It can take up to ten (or more) HDDs to match the performance and density of a single SSD, so you would have to multiply the price of the HDD to provide an accurate comparison. In either case, SSDs win the competition easily. All of the major OEMs are also moving on to flash-centric architectures, so the lengthy 15K HDD OEM supply agreements have dwindled, thus removing the lion's share of the 15K HDDs addressable market.

The SSD clock was ticking, but now the alarm is going off. Let's take a look at Seagate's last 15K HDD.

Seagate Enterprise Performance 15K HDD v6

Seagate's last generation of 15K HDDs do come with a nice smattering of technology that yields impressive performance gains over previous generations; Seagate claims it is the fastest 15K HDD on the market. The 15K.6 provides up to 315 to 215 MB/s (outer to inner) of sustained throughput, which handily beats the current crop of 15K HDDs.

Seagate Enterprise Performance 15K v6 4Kn Models
Average Latency
2.0 ms
2.0 ms
2.0 ms
Sustained Transfer Rate (Outer to Inner)
315/215 MB/s
315/215 MB/s315/215 MB/s
Cache (Multisegmented)
12Gb/s SAS
12Gb/s SAS12Gb/s SAS
TurboBoost Read Caching (SKU)
Advanced Write Caching (AWC)
Avg Operating Power
Typical Operating Power

The 12 Gb/s SAS 15K.6 comes in capacities of 300GB, 600GB, and 900GB with a 2.0ms average latency. The platter and head count vary based upon capacity. From an architectural standpoint, the drives bring the best of HDD engineering to bear, including Seagate's TurboBoost SSHD technology, which uses a small 16GB NAND buffer to increase read workload performance in some environments. SSHDs really haven't taken off in either the enterprise or the client segment, and other vendors have avoided the practice. Seagate offers the TurboBoost models as separate SKUs.

The 15K.6 also wields a 256MB DRAM cache to speed operations, along with up to 8MB of NVC-backed (Non-Volatile Cache) write cache (likely with NOR) to power Seagate's (AWC) Advanced Write Caching feature. AWC is a new performance-boosting caching implementation that provides explosive performance gains (well, in terms of HDDs) for random write data. HGST began the trend of using non-volatile backed cache to provide increased random write performance with its media caching technology, and we expect Toshiba to follow suit. The 15K HDDs are receding into the background, but the new technologies that were proven on the platform live on in the standard 3.5" high-capacity models.

Power consumption varies by capacity, as listed in the table, but it's notable that it isn't especially competitive with SSDs. The 15K.6 comes with SED and FIPS 140-2 models for the security conscious, and Seagate also offers a Fast-Format feature that allows vendors to switch 4Kn/512e formatting on the fly. The company also offers dedicated 512n and 4Kn/512e models as separate SKUs.

The Flash-Powered Future

The 15K's overdue demise isn't entirely unexpected; in fact, we've been expecting it for some time as the HDD vendors retreat into the "cheap and deep" space with their high-capacity 3.5" HDDs in tow. The mission-critical 10K HDD segment continues to find success; most OEMs have long advised their users to select 10K HDDs over 15K models. However, the SSD clock is ticking for the 10K segment as well, but we aren't able to confirm if vendors are on their last generation of those venerable models or not.

Seagate continues to reap the fruits of its strategic alliance with Micron that finds the two companies releasing the exact same SSD hardware under different names. We expect that initiative to gain steam as Seagate segues from 15K HDDs into the SSD market. Samsung has plundered the competition and is currently in the driver’s seat for data center SAS SSDs, largely on the back of its 3D NAND advantage.

HGST and Intel had an SAS SSD partnership for several years that delivered industry-leading products, but now that WD has purchased SanDisk, it appears that the fruitful relationship ended on a sour note. In either case, WD is currently the best-positioned enterprise SSD/HDD vendor with its powerful cornucopia of products, and if it can get its BiCS 3D NAND to market in a somewhat timely manner, we expect it to gain share quickly.

In some respects, Seagate is on the outside looking in on the flash market; its two primary rivals (WD and Toshiba) have NAND fabs, and it does not. The stand-offish strategy does not bode well for a company that is obviously ceding market segments to SSDs, and many expect Seagate to buy or merge its way into a NAND fab (my bet is on Micron).

The Seagate Enterprise Performance 15K HDD v6 is available now for technology laggards, and it carries the enterprise-standard five-year warranty.

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  • takeshi7
    One of the advantages 15K HDDs have over SSDs that you failed to mention in the article is the write endurance is much higher for an HDD.
  • PaulAlcorn
    1481619 said:
    One of the advantages 15K HDDs have over SSDs that you failed to mention in the article is the write endurance is much higher for an HDD.

    Well, here is an oddity... that common belief is both right and wrong.

    It all boils down to how much data you can actually write to the drive. This is called usable endurance. HDDs are so slow that they cannot write enough data over their lifespan to compete. Here is an excerpt from another site where I wrote a post covering this topic in 2013. The numbers are probably even more in favor for SSDs with the newer models.

    "While crunching the numbers it occurred to me that endurance isn't quite as clear-cut as one would expect. Taking a look at an entry-level SSD we see that an endurance of 3 DWPD (Drive Writes Per Day) is pretty standard for a random workload. The sequential workload endurance can be much higher, from 7-10 DWPD, depending upon the SSD. While the glass platter substrate of an HDD has a very high tolerance for heavy workloads, the mechanics of the moving parts conspire to hinder the speed, and thus the useable endurance of the drive. In our testing, the fastest 15K HDDs write at a speed of roughly 450 IOPS for both 4K and 8K random write workloads. For 4k this equates to roughly 148 GB's of data written per day. For 8K access, common to many server workloads, we arrive at roughly 296 GB of potential data written per day.

    An entry-level SAS SSD, by comparison, can provide over 30,000 IOPS of 4k write speed and 18,000 8K write IOPS in steady state. This equates to nearly 9.6 TB of potential data writes per day for 4K access, and 11.5 TB's per day for 8K write access. This is a huge advance over the HDD, and could necessitate throttling of the SSD to keep it within the expected warrantied workload of 3 DWPD. With the capacity of new SSDs touching 2TB, this can provide up to 6 TB of useable endurance per day for the SSD, in comparison to the lowly 148-296 GB attainable by today's fastest HDDs.

    The 2TB SSD can provide 10,950 TBs of 8K write activity (endurance) over the warrantied period of five years, compared to the HDD with 534 TBs.

    The slower speed of the HDD negates its ability to take advantage of its nearly-unlimited endurance, while the SSD can write nearly 20X more data over five years.

    In a nutshell, SSDs offer up to 20X (and even more) usable endurance than HDDs.
  • PC-Cobbler
    Seagate buy Micron? Not likely, given that Micron is bigger in every monetary respect. SK Hynix would be a possibility, but South Korea's chaibol culture might prevent that. I think it's much more likely for Seagate to partner with a Chinese fab, given its close ties to China (Seagate's job listings often ask for people who speak fluent Mandarin). Another possibility is Seagate being bought by a Chinese company such as Tsinghua or XMC.