We've tested a ton of SandForce-based SSDs, and we know that drives utilizing the same NAND interface perform similarly, regardless of brand. As a result, we're representing SandForce's second-gen controller by publishing results from OCZ's Vertex 3, which is analogous to Intel's SSD 520 and Corsair's Force GT. All three drives employ synchronous memory.
We're also preconditioning each SSD prior to random and sequential read testing. This helps us address a potential issue whereby a drive's flash translation layer could return a read request without actually accessing data after a secure erase. This should help put our SSDs on a more level playing field.
Random Read Performance (background info)
At a queue depth of one, nearly every SSD delivers ~20 MB/s in random reads. However, as we scale up to four outstanding I/O requests, we start to see the results spread out a bit. The 840 Pro continues to distinguish itself at a queue depth of 16, though, and starts to approach 400 MB/s (or nearly double the speed of Crucial's 256 GB m4 and OCZ's 240 GB Vertex 3).
Just as important, the 840 Pro delivers a nearly-30% performance increase over the 830. We couldn't get Samsung to get specific about a lot of what's going on under the hood, but the company certainly does appear justified in designating a new high-end SSD based on the changes it made.
Random Write Performance
The lines are bunched closer together and intersect more often in our random write test. Every SSD delivers between 60-70 MB/s at a queue depth of one. At a queue depth of four, the field spreads out, but then mixes up a bit during the increase to seven outstanding commands. By then, Samsung's 840 Pro takes the lead, delivering ~350 MB/s (~90 000 IOPS). It remains there all the way through the rest of the test.
In the past, we've seen Samsung's drives perform poorly in random write tests. It was an issue for the 470, and we saw it again from the 830, which hangs toward the bottom of this chart. The fact that the 840 Pro rectifies this means the biggest weakness from previous generations is being addresses effectively.