Incompressible Performance: SandForce's Weakness
The preceding page represented a best-case scenario for how SandForce's SF-2281 controller handles your information. Specifically, we know it handles compressible data very efficiently. But the company freely admits that it's not as deft when forced to address incompressible information. The cornerstone of its DuraClass engine centers on the premise that the majority of your desktop workload is, in fact, compressible. Nevertheless, there are still plenty of workloads that incorporate incompressible data.
Incompressible Sequential Read
In this specific scenario, OCZ's drive manage to move about 100 MB/s more than Intel's at a queue depth of one. At higher queue depths, that advantage disappears.
Our NTFS-formatted PC exhibits overhead we didn't see when we were testing the physical blocks. Performance starts in the 300 MB/s range and scales up from there. As we'd expect, the 60 GB drives tend to be a little slower than the 240 GB models.
The Mac behaves differently. This time, performance at low queue depths is higher. The lower-capacity 60 GB drives take more of a hit than the 240 GB drives, though. Interestingly, this is one occasion where the 60 GB SSD 520 outperforms OCZ's 60 GB Vertex 3.
Incompressible Sequential Write Performance
Writing incompressible data sequentially is more of a challenge than reading. Intel establishes a small, yet quantifiable advantage in this discipline. Its SSD 520s consistently outperform the Vertex 3s by 5-8 MB/s, and this modest delta translates to the Mac and PC tests below.