Results: Tom's Hardware Storage Bench, Continued
Service Times
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 latency 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 storage device, and have the drive acknowledge the operation. Read latency is similar. The operating system asks the storage device for data stored in a certain location, the SSD reads that information, and then it's sent 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.
OCZ's refreshed Vector drive falls behind even the Vertex 450 in terms of write latency, though that margin is imperceptible, and only something we pick up due to the righteously large nature of this chart. Remember, the further south and west a drive appears, the better.
And yes, once again, the Vector 150 falls right between the Vector and Vertex 450. Not highlighted, but also of interest, OCZ's Vertex 3.20 240 GB appears just below the Vertex 450 in our trace's read service times, but far behind in writes. Both of those drives employ 20 nm ONFi NAND, though the Vertex 450 gets the advantage of a different processor and OCZ's performance mode/storage mode technology.
I'm highlighting all of the OCZ drives, but it's easy to imagine where the drives fall without the entirety of this chart. The Vertex 3.20 shows up right in the middle of the field, a few thousandths of a second per I/O behind the Vertex 450, which in turn is a few thousandths behind the Vertex 150. In second place, just behind Samsung's magnum opus, is the original Vector.
Mean write service times are more varied, resulting in more separation in the chart at the top of this page. It's telling that the podium is dominated by OCZ, with the Vector and Vertex 450 followed by its new Vector 150. The gold, silver, and bronze contenders aren't distinguished by much, but a difference does exist.
