It’s common knowledge that the appearance of consumer oriented Solid State Drives (SSDs) revolutionized the storage industry but even after several years in the market their price/capacity ratio is nowhere close to the one of regular mechanical drives and that’s something that drives away casual consumers who are not really interested in getting the highest possible performance levels. Well because manufacturers know how the market works the next obvious step for them was to somehow marry the high performance levels of SSDs with the capacity of regular HDDs in order to dish out something just as fast but with higher capacity and lower price and out of that marriage hybrid drives were born. Unfortunately although the first attempts did offer some performance improvements at roughly the same price as regular HDDs they weren’t very successful in convincing consumers that this was the way to go.
SSHD IS THE LATEST BUZZWORD in the PC storage industry. Although the branding is fresh, the term refers to a class of products that’s been around for quite some time. Otherwise known as solid-state hybrid drives, SSHDs combine mechanical platters with flash-based SSD cache memory. Thanks to technologies such as Triple Level (TLC) cells and vertically stacked chips, SSDs keep getting bigger (the largest consumer SSD is now 2TB), but the cost per GB of an SSD is still considerably higher than in mechanical disks and will likely remain so for a long time. Hybrid drives aim to be the best of both worlds in giving you the capacity of a mechanical hard disk combined with some of the speed advantages of an SSD. They first popped up in the Windows Vista era and were designed to work with that operating system’s ReadyDrive feature. Vista wasn’t exactly popular at the time, and hybrids faded into obscurity. [You may want to check our best hybrid hard drive list]
Like all standard SSHDs, the Seagate solution takes the massive capacity of a mechanical hard drive and adds NAND flash to it, allowing the drive to use a proprietary caching algorithm to speed up frequently used applications. The Seagate Desktop SSHD hybrid is the first desktop 3.5″ form factor, 6Gb/s SATA interface drive. Seagate claims the SSHD hybrid will increase system performance by up to 4x faster than standard 7,200 RPM HDD by using adaptive memory technology that learns the data users access most frequently and adds it to the solid-state memory for instant access.
Seagate revisited the idea in 2011 with the Momentus XT notebook drive. This hybrid solution was independent of the OS, instead relying on drive-level intelligence to manage the flash. All things considered, it was a pretty good compromise for notebooks. A second generation Momentus XT hybrid followed the initial model, and the third iteration of the platform debuted with the SSHD moniker earlier this year.
While mobile users have had access to Seagate hybrid drives for a long time, up until now desktop users had to choose between the superior speed of SSD versus the relatively inexpensive storage space of HDD (or some combination of both). When the latest batch of notebook-bound SSHDs was introduced, Seagate revealed that a desktop version would soon join the family. This simply named Desktop SSHD would discard the 2.5″ form factor of previous hybrids in favor of a larger 3.5″ body packed with up to 2TB of 7,200-RPM mechanical storage. The Seagate Desktop SSHD Hybrid theoretically gives users the best of both worlds. Whether you’re a gamer with hundreds of games, a business that uses multiple large programs, or just a music and movie buff that has thousands of both, with the SSHD Hybrid you won’t have to sacrifice speed for storage or storage for cost and the solution is easy to deploy, no additional software or configuration is required. [You may check either of our lists: the best hard drive (HDD) for gaming or the best desktop SSHD]
Design & Features
The Seagate Desktop SSHD Hybrid features the same design as their other desktop hard drives (Seagate Barracuda and Seagate HDD 1.5). The top cover is silver containing the relevant product information. The body of the drive is black metal.
At the heart of the Seagate Desktop SSHD is a LSI disk controller paired with an eASIC SSD controller that leverages the on-board 8GB Toshiba MLC NAND.
The SSD cache of the device is, once again, 8 GB in size. The PCB features a single Toshiba MLC flash module, which internally consists of two dies. Seagate controls one part of the chip in MLC mode (2 bits per cell), and another part in SLC mode (1 bit per cell), the latter of which allows for lower latencies and higher endurance. The exact MLC/SLC ratio and whether or not a constant ratio is used is unclear: Seagate is not particularly forthcoming with technical details to the press. For those who are at all concerned about the flash chip’s lifespan: Seagate indicates that it is twice as long as what would be required for five years of “standard usage”, although they did not specify what standard usage exactly entails.
While the disks of the Desktop SSHD 1TB and 2TB run at 7200 rpm, the disks in the 4TB model are limited to 5900 rpm. As such, with the 4TB model we are basically dealing with an SSHD variant of the Seagate Desktop HDD.15 4TB.
The 4TB Desktop SSHD is manufactured with four platters encompassing eight heads with a load/unload cycle rating of 300,000. Power consumption of the drive is set at 7.5 watts operating, with idle hovering around 6.2 watts. Sleep and standby power are both set at 0.75 watts.
Just like the 2TB model, the 4TB model’s SSD cache features a maximum read speed of 190 MB/s. In the 4TB model the average seek for read and write is listed as less than 12ms and the average read speed of the magnetic disks is a little bit lower than for the 2TB model at 146 MB/s over the platters, which can be explained by the lower rotational speed, and increases to 190 MB/s when reading from the NAND. Again, we must conclude that the advantage of the SSD cache does not lie in the increased transfer rates, but rather, in the greatly decreased access times.
According to Storage Review website testing team, they found the SSHD to offer a boost in performance across all workload-types in a “cached” setting with a 5GB hot data zone. Limiting current Desktop SSHDs to only 8GB of NAND flash does limit how many applications will fit inside cache, although increasing the amount of NAND would undoubtedly increase the cost and nudge users to consider a full SSD instead. Comparing raw performance, cached versus uncached offered 2-3x gains, giving users the performance of a 10K HDD for cached items. This falls quite a bit short of full SSD performance which is orders of magnitude higher, but still measureable gains.
As for the Tweak Town team, they found the 4TB SSHD to scale quite well in random read operations, while random write carried a burst of performance followed by linear results around 330 IOPS. Sequential read performance was a bit of a misnomer for both the 2TB and 4TB SSHDs as it reached only 55 MB/s. Write performance on the other hand was chart topping at 177 MB/s, beating out the 2TB solution by 20 MB/s.
Workload testing was up and down for the 4TB SSHD, as the database workload presented a challenge for the SSHD. However, throughout the rest of workload testing, the 4TB SSHD was at the top of the charts and cemented itself as a great workstation solution reaching 202 IOPS at QD32. Power testing revealed the 4TB SSHD used a just a touch more power than the standard solution in random read and write, while sequential workloads had each of the drives within 0.14 watt of each other.
It is hard to verify the real advantage of a hybrid hard disk drive. Synthetic tests do not take advantage of the SSD portion, since the drive controller only places data there after it “learns” its frequently accessed data. But even in those tests, the Seagate Desktop SSHD TB unit did not disappoint, being faster than a similar conventional hard disk drive in several tests.
For desktop computers, the combination of an SSD for OS + programs and a conventional hard drive for data remains the best choice, as far as we’re concerned. The added value of an SSHD for this usage model is limited, but luckily, the premium above a conventional hard drive is also rather small. When your budget is too small to include both an SSD and an HDD, using a single SSHD will be a far better solution than using a single conventional hard drive as your only storage device.