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.
There is more variability between the three 180 GB SSDs from Intel than you might have expected. Across our 16 GB active test range, the SSD 530 achieves about 45,000 IOPS with compressible data. Roughly 35,000 4 KB IOPS is the best we can hope for testing incompressible data. Intel says its SSD 530 is good for 41,000 4 KB read IOPS at a queue depth of 32. We beat that number using compressible information, but don't quite get there pushing random payloads.
Interestingly, note that the diminutive SSD 525 beats the rest of the field.
4 KB Random Writes
Random write performance is also exceptionally 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, but there's a point of diminishing returns in desktop environments.
When you swap a hard drive out for solid-state storage, your experience improves. Load times, boot times, and system responsiveness all get better. When it's called upon, your SSD can handle a lot more I/O than the spinning media you had in there before. When it comes to typical client workloads however, getting to those operations faster is what matters, not necessarily trying to juggle more of them.
Intel's SSD 520 replacement delivers the 80,000 IOPS it's rated for, but only when we send compressible data down its channels. Repeating information is supremely easy for SandForce's real time data deduplication technology to manage, which is why we see the higher numbers. With random data coming out of the buffer, the SSD 530 goes so far as to surpass our expectations with 55,000 IOPS.
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 180 GB SSD 530 posts respectable numbers, even if they don't top our chart. Isolating repeating data, the SSD 530 places under the 120 GB SanDisk Extreme II and 128 GB Silicon Motion SM226EN. It even slots in under the older SSD 520 and 525. Testing with random data, it finishes just ahead of Intel's Marvell-powered SSD 510. That means it's even behind SanDisk's Ultra Plus 64 GB.