We’ve talked about how good these drives are compared to normal hard drives. But the extent to which these SSHDs excel over their popular counterparts will be made evident after this article. If you’ve gone through the previous articles then you’d know that these SSHDs are a hybrid construction of mechanical hard drives and SSDs. To be more specific they are every bit a normal hard drive but they feature an 8GB NAND cache memory with adaptive learning. The most commonly used files are cached onto the 8GB NAND memory so that the next time a read request is entertained for the said files they are fetched from the cache memory which is much faster. Let’s take a look at the specifications of a 2TB SSHD we’re going to be putting through the tests.
Seagate Desktop SSHD Hybrid Specification
- 2TB (ST2000DX001)
- 2x1TB platters
- 2TB (ST2000DX001)
- Interface: SATA 6Gb/s
- Spindle: 7,200 RPM
- Cache: 64MB
- NAND Cache: 8GB MLC
- Average Data Rate from NAND: 190 MB/s
- Average Data Rate: 158 MB/s
- Average Latency: <12ms
- Operating: 2TB 6.7W
- Idle: 2TB 3.6W
- Operating Temperature 0° to 60°C
- Non-operating Temperature -40° to 70°C
- Dimensions (L x W x H):
- 2TB 146.05mm x 101.6mm x 26.11mm
- 2TB 408g (0.90lbs.)
First off, we’re going to be comparing the 2TB SSHD with a normal 4TB hard drive. Both are rated for 7200 RPM but only the SSHD has the advantage of having the 8GB NAND cache memory and it shows. SiSoft Sandra pegs the SSHD at a minor advantage over the normal hard drive both in terms of access time and also read speed. The 4TB normal hard drive managed to get 138 MBps read speed while the SSHD managed to hit 158.57 MBps. The access time was 13.74 milliseconds for the normal hard drive and 11 milliseconds for the SSHD.
HD Tune Pro
HD Tune is known for its intensive tests that involve going through each and every sector of the platter one by one to chart the specifications across the entire capacity of the hard drive. We compared the two drives on 4 parameters viz., IOPS (Read and Write), Average Access Time (Read and Write). We found that the SSHD performed better than the normal hard drive across all four of these parameters. The performance disparity was enough to chart the results around the 50% mark for the normal hard drive. Looking at the actual numbers may make things more clear. The IOPS (read) score was 39 and 47 for the normal hard drive and the SSHD respectively. The IOPS (write) score stands at 54 and 60 for the same set. These are score and not the actual IOPS figures.
Adaptive learning is the ability of an SSHD to figure out which files are in frequent use and then cache them so that subsequent access requests to the file are entertained much faster. This means that when multiple runs are performed the SSHD starts performing better and better. Let’s check this out by running the same HD tune test twice. The second time around the scores improve. In the graph below, the second run scores out perform all the other scores so we kept that as the base. We can see that the Write access times are the same for both runs but everything else has experienced a significant improvement. The read speed went from 159.8 MBps on the first run to 176 MBps on the second run. Access read time went from 14.4 milliseconds to 7.7 milliseconds on the second run.
Looking at the synthetic benchmarks we can say for sure that an SSHD performs better than a normal hard drive across all aspects. Sure an SSD does way better but does it give you good returns for your investment? Not at all. SSHDs are competitively priced when compared to normal hard drives but SSDs are way too expensive. In the next set of articles we shall be looking at more applications which shall be used to compare these different technologies against each other.