Incompressible Performance: SandForce's Weakness
SandForce's SF-2281 controller handles compressible data very effectively, and the preceding page illustrates its best-case behavior nicely. However, the controller vendor openly admits that performance drops when it comes to addressing incompressible information. The proprietary DuraClass engine was designed under the assumption that most data is compressible. However, there are still plenty of workloads that involve incompressible information, too.
Incompressible Random Writes
At a queue depth of one, all of the SSDs achieve transfer rates between 50 and 60 MB/s. But once Iometer scales up to eight or more outstanding I/O operations, the drives differentiate themselves a little more clearly.
The SSD 520 leads by hitting 250 MB/s at a queue depth of 16, followed by Intel's SSD 330 and Monster's Daytona. Meanwhile, the SSD 335 only manages to match Crucial's m4, not quite reaching 200 MB/s.
Incompressible Sequential Write Performance
Although performance doesn't really improve as queue depth increases, the finishing order of the SandForce-based drives is fairly similar to what we saw in the random writes. Mainly, Intel's SSD 520 is up top, followed closely by the SSD 330, SSD 335, and Monster Daytona.
Samsung’s 840 Pro continues to lead the charge, sustaining close to 550 MB/s from a queue depth of two. When you compare the data from this page to the previous page, we see that it doesn't matter what kind of data you move with the 840 Pro; performance is gloriously consistent.