Results: Tom's Hardware Storage Bench v1.0, Continued
Beyond the average data rate reported on the previous page, there's even more information we can collect from Tom's Hardware's Storage Bench. For instance, mean (average) service times show what responsiveness is like on an average I/O during the trace.
It would be difficult to graph the 10+ million I/Os that make up our test, so looking at the average time to service an I/O makes more sense. For a more nuanced idea of what's transpiring during the trace, we plot mean service times for reads against writes. That way, drives with better latency show up closer to the origin; lower numbers are better.
Write service time is simply the total time it takes an input or output operation to be issued by the host operating system, travel to the storage subsystem, commit to the device, and have the drive acknowledge the operation. Read service is similar. The operating system asks the storage device for data in a certain location, the SSD reads that information, and then sends it to the host. Modern computers are fast and SSDs are zippy, but there's still a significant amount of latency involved in a storage transaction.
As you look through the results, note that any time we get four capacities from the same product family, it's not uncommon for there to be a big delta between the smallest and largest models.
And indeed, the spread is more significant than I would have expected given two capacities and different NAND interfaces.
Mean Read Service Time
By now, we've come to expect the L85A/L85C-equipped configs pulling up the rear. On the other hand, the reference JMF667H-based SSDs with Toggle-mode NAND look hot. Both capacities are split by the M5 Pro, and they finish ahead of Adata's zippy SP920 at 512 GB.
Those read service times are only slightly related to capacity though, whereas write service times correlate more closely.
JMicron's L85C-based 128 GB drive beats out the 120 GB M500, while the 128 GB JMicron drive with A19 flash falls behind Silicon Motion's reference platform by a slim 11-microsecond average.