Results: 4 KB Random Performance
We turn to Iometer as our synthetic metric of choice for testing 4 KB random performance. Technically, "random" translates to a consecutive access that occurs more than one sector away. On a mechanical hard disk, this can lead to significant latencies that hammer performance. Spinning media simply handles sequential accesses much better than random ones, since the heads don't have to be physically repositioned. With SSDs, the random/sequential access distinction is much less relevant. Data are put wherever the controller wants it, so the idea that the operating system sees one piece of information next to another is mostly just an illusion.
4 KB Random Reads
Testing the performance of SSDs often emphasizes 4 KB random reads, and for good reason. Most system accesses are both small and random. Moreover, read performance is arguably more important than writes when you're talking about typical client workloads.
Whether it's the controller's higher clock rate, the faster NAND interface, or a combination of both, the SSD 730 Series 480 GB ends up holding a good 10,000 IOPS over the SSD DC S3500 and S3700.
4 KB Random Writes
Random write performance is also important. Early SSDs didn't do well in this discipline, seizing up even in light workloads. Newer SSDs wield more than 100x the performance of drives from 2007, though we also recognize that there's a point of diminishing returns in desktop environments.
We see the same outcome here, except the SSD 730 Series peaks almost 33% higher than the SSD DC S3700 and a little under that over the S3500.
Random Performance Over Time
My saturation test consists of writing to each drive for a specific duration with a defined workload. Technically, it's an enterprise-class benchmark, where the entire LBA space of the SSD is utilized by a random write at high queue depths. But that's relevant here, since the SSD 730 Series drive has enterprise-class roots.
This is 12 hours of a 4 KB write with 32 outstanding commands. First, we secure erase each drive. Then, we apply the 4 KB write load, showing the average IOPS for each minute (except for the last 20 minutes, where we zoom in and show you one-second average increments).
After the first drive fill, performance drops off fast because the SSD 730 doesn't have any more free blocks to write to. Rather, old blocks have to be erased prior to subsequent writes. Nevertheless, Intel's drive starts off stoutly. The company's goals with its SSD DC S3700 were low write amplification accompanied by high steady state write performance and latency confined to a narrow range.
Those first two are of less concern on a client drive. Intel likely anticipates that most of the pounding applied to its SSD 730 will come from high-res video, after all.
The SSD DC S3700 employs a good deal more over-provisioning and better flash, leaving its SSD DC S3500 and SSD 730 much more similar (aside from the fancy firmware and overclocked components). That's good enough for a steady state 12,000 IOPS, measured in one-minute averages, though. This is a respectable number from a client drive. Obviously sacrificing more usable capacity for better steady state speed would help. But in this case, it's wholly unnecessary.
When I slice out a chunk of that line graph to observe one-second intervals, another story materializes. I've gone a step further to generate 100% write numbers (in pink), 50% reads and 50% writes (in green), and 70% reads and 30% writes (in blue). Clearly, the pink bar is at the bottom. With such a disparity between read and steady state write performance, the more write I/Os in the mix, the lower you'll see performance dip. To that point, a mix of 50/50 yields about 25,000 IOPS, while the 70/30 gives you around 40,000. But all three mixes of reads and writes exhibit the same limited spread as the more data center-oriented SSDs, with little variation from minimum to maximum. Like a marksman, the SSD 730 Series manages remarkably tight groupings for a client drive. This is especially awesome in a striped array, where the entire configuration is only as fast as its slowest member.
Here's a break-down of the maximum observed 4 KB sequential read and write performance with Iometer. The order the drives appear in our chart is determined by maximum combined read and write performance.
The 480 GB SSD 730 falls in amongst the top tier of mainstream drives. Maximum IOPS isn't the surest indicator of performance, which is why we use so many other tests to characterize speed as well. If you're going to sell a drive on its raw, unadulterated performance, though, you'd better be sure that SSD delivers.
