Mixed Workloads And Steady State
80 Percent Sequential Mixed Workload
Several of the TLC-based SSDs struggle with sequential mixed workloads. SATA is a half-duplex interface, so it can't read and write at the same time. Native command queuing was implemented to help mixed workload performance by stacking and running operations in an optimized order.
80 Percent Random Mixed Workload
Those performance issues apply to random transfers as well, and are compounded by the small 4KB blocks we're moving around.
Sequential Steady State
The upswing we see when the graph gets to 100 percent sequential writes shows just how much Phison has improved performance with TLC flash. If you look back at the Adata SP550 review, there are several examples of what we more commonly associate with TLC in steady state using the same test. After the 80 percent read measurement, most TLC-based drives level out under 100 MB/s and never recover. Not only does the BP5e stage a recovery, but it also keeps performance north of 200 MB/s through most of our benchmark.
Random Write Steady State
There are two interesting take-aways, one from each random steady state chart. In the first test, where we see preconditioning happen before the measurement, the BP5e has two towering spikes where the SLC buffer flushes and then starts accepting 4KB blocks again. In the second chart, we see the BP5e drop to very low levels. Unlike the 960GB OCZ Vector 180, MyDigitalSSD's drive does not fall to zero (though it does dip to around 250 IOPS, about the same as a high-performance mechanical disk). Fortunately, you will never see a steady state condition under random I/O without running a database server on the drive.