Our IOMeter workloads feature a ramping number of concurrent I/O requests. Most desktop systems will only have a few requests in flight at any given time (87% of DriveBench 2.0 requests have a queue depth of four or less). We've extended our scaling up to 32 concurrent requests to reach the depth of the Native Command Queuing pipeline associated with the Serial ATA specification. Ramping up the number of requests also gives us a sense of how the drives might perform in more demanding enterprise environments.
We run our IOMeter tests using the fully randomized data pattern, which presents a particular challenge for SandForce's write compression scheme. We'd rather measure SSD performance in this worst-case scenario than using easily compressible data.
There's too much data to easily show on a single graph for each access pattern, so we've once again split the results by drive maker. You can compare the Samsung 840 Pro Series' performance to that of the competition by clicking the buttons below each graph.
We'll start with the web server test, which consists of read operations exclusively. Here, the 840 Pro achieves higher I/O throughput than not just the other Samsung SSDs, but also everything else.
The 840 Pro largely retains its lead over the other Samsung SSDs in the file server, database, and workstation tests, all of which mix read and write operations. However, the vanilla 840 Series boasts higher transaction rates with the heaviest loads in the file server and database tests. The 840 Pro's performance actually drops between 16 and 32 concurrent I/Os in those tests, behavior that matches that of the old 830 Series. For some reason, the drop-off doesn't affect the 840 Pro in the workstation test. Samsung's newer firmware doesn't have any impact, either.
Versus its SandForce-based rivals, the Samsung 840 Pro Series sticks close with lighter loads but crunches more I/Os as the number of concurrent requests ramps up beyond four. OCZ's Vector and Vertex 4 provide stiffer competition under those more strenuous loads. The Corsair Neutrons offer much higher transaction rates across the board in all three tests, though.